Doppler mode in a wireless network

ABSTRACT

To receive data in data field of a PHY Protocol Data Unit (PPDU), wherein the data field includes mid-ambles, a number of mid-ambles and a number of data symbols included in the data field is determined. The number of mid-ambles is determined according to information in an HE-SIG-A field of the PPDU, information in an L-SIG field of the PPDU, and one or more predetermined values prescribed by a standard. The number of data symbols may be determined using the number of the mid-ambles, and the data received according to the number of mid-ambles and the number of data symbols.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 62/511,914, filed May 26, 2017, which is incorporated byreference herein in its entirety.

BACKGROUND 1. Technical Field

The technology described herein relates generally to wirelessnetworking. More particularly, the technology relates to determiningparameters of a received transmission wherein mid-ambles are used toimprove the reception of the transmission.

2. Description of the Related Art

Wireless Local Area Network (WLAN) devices are currently being deployedin diverse environments. Some of these environments have large numbersof access points (APs) and non-AP stations in geographically limitedareas. In addition, WLAN devices are increasingly required to support avariety of applications such as video, cloud access, and offloading. Inparticular, video traffic is expected to be the dominant type of trafficin many high efficiency WLAN deployments. With the real-timerequirements of some of these applications, WLAN users demand improvedperformance in delivering their applications, including improved powerconsumption for battery-operated devices.

A WLAN is being standardized by the IEEE (Institute of Electrical andElectronics Engineers) Part 11 under the name of “Wireless LAN MediumAccess Control (MAC) and Physical Layer (PHY) Specifications.” A seriesof standards have been adopted as the WLAN evolved, including IEEE Std802.11™-2012 (March 2012) (IEEE 802.11n). The IEEE Std 802.11 wassubsequently amended by IEEE Std 802.11ae™-2012, IEEE Std802.11aa™-2012, IEEE Std 802.11ad™-2012, and IEEE Std 802.11ac™-2013(IEEE 802.11ac).

Recently, an amendment focused on providing a High Efficiency (HE) WLANin high-density scenarios is being developed by the IEEE 802.11ax taskgroup. The 802.11ax amendment focuses on improving metrics that reflectuser experience, such as average per station throughput, the 5thpercentile of per station throughput of a group of stations, and areathroughput. Improvements may be made to support environments such aswireless corporate offices, outdoor hotspots, dense residentialapartments, and stadiums.

In some environments, channel conditions may change during thecommunication of a data unit. For example, when non-AP stations aremoving with respect to the AP, the Doppler effect may alter the channelconditions. In these environments, mid-ambles may be inserted in a dataportion of a communication to allow channel estimation to be performedby the receiving device during the reception of the data portion. Thepresence of mid-ambles into the data portion may alter how the receivingdevice determines some of the parameters of the communication.

SUMMARY

In an embodiment, a method performed by a wireless device comprisesreceiving a first portion of a PHY Protocol Data Unit (PPDU), the firstportion including a Legacy Signal (L-SIG) field, decoding the L-SIGfield, and determining a format of the PPDU using the first portion. Inresponse to determining that the format of the PPDU is a High Efficiency(HE) format, the method performs receiving and decoding an HE Signal A(HE-SIG-A) field, and determining, using a Doppler field of the HE-SIG-Afield, whether the PPDU includes mid-ambles. In response to determiningthat the PPDU includes mid-ambles, the method performs determining,according to the format of the PPDU and using first informationdetermined using the HE-SIG-A field and second information determinedusing the L-SIG field, a number of mid-ambles N_(MA) indicating thenumber of mid-ambles included in a data field of the PPDU, determining,using the number of the mid-ambles N_(MA), a number of data symbolsN_(SYM) included in the data field of the PPDU, and receiving, using thenumber of mid-ambles N_(MA) and the number of data symbols N_(SYM), thedata field of the PPDU.

In another embodiment, a wireless device comprises a receiver and aprocessor. The processor is configured to perform receiving, using thereceiver, a first portion of a PHY Protocol Data Unit (PPDU), the firstportion including a Legacy Signal (L-SIG) field, decoding the L-SIGfield, and determining a format of the PPDU using the first portion. Theprocessor is further configure to, in response to determining that theformat of the PPDU is a High Efficiency (HE) format, perform receivingand decoding an HE Signal A (HE-SIG-A) field, and determining, using aDoppler field of the HE-SIG-A field, whether the PPDU includesmid-ambles. The processor is further configure to, in response todetermining that the PPDU includes mid-ambles, perform determining,according to the format of the PPDU and using first informationdetermined using the HE-SIG-A field and second information determinedusing the L-SIG field, a number of mid-ambles N_(MA) indicating thenumber of mid-ambles included in a data field of the PPDU, determining,using the number of the mid-ambles, a number of data symbols N_(SYM)included in the data field of the PPDU, and receiving, using the numberof mid-ambles N_(MA) and the number of data symbols N_(SYM), the datafield of the PPDU.

In embodiments, the first information includes a Packet Extension (PE)Disambiguity bit value b_(PE-Disambiguity), a number of HE Long TrainingFields (HE-LTFs) value N_(HE-LTF), an HE-LTF duration including guardinterval T_(HE-LTF), and a data symbol duration T_(SYM), and a mid-ambleperiodicity M.

In embodiments, the first information further includes a preambleduration T_(PA) according to the format of the PPDU, the HE-LTF durationT_(HE-LTF), and the number of HE-LTFs value N_(HE-LTF).

In embodiments, the first information further includes a mid-ambleduration T_(MA).

In embodiments, the second information includes a Length field valueL_LENGTH.

In embodiments, determining the number of mid-ambles N_(MA) includesdetermining the number of mid-ambles N_(MA) according to:

$N_{MA} = \left\lfloor \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}Disambiguity}} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rfloor$wherein m is 1 when the format of the PPDU is an HE Multi-User PPDU orHE Extended Range Single User PPDU format and m is 2 otherwise, andwherein β is an integer number greater than or equal to zero.

In embodiments, determining the number of mid-ambles N_(MA) includesdetermining the number of mid-ambles N_(MA) according to:

$N_{MA} = \left\lceil \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}Disambiguity} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rceil$wherein m is 1 when the format of the PPDU is an HE Multi-User PPDU orHE Extended Range Single User PPDU format and m is 2 otherwise, andwherein β is an integer number greater than or equal to zero.

In embodiments, β is 1.

In embodiments, receiving the data field comprises repeating, a numberof times equal to the number of mid-ambles N_(MA), the steps of:receiving a plurality of consecutive data symbols, wherein the number ofdata symbols in the plurality of data symbols is equal to the mid-ambleperiodicity M, and receiving a mid-amble immediately following theplurality of consecutive data symbols. Then the embodiment receives aremaining 0 or more remaining consecutive data symbols, wherein thenumber of data symbols N_(remain) is equal to:N _(remain) =N _(SYM)−(M·N _(MA))

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless network, according to an embodiment.

FIG. 2 is a schematic diagram of a wireless device, according to anembodiment.

FIG. 3A illustrates components of a wireless device configured totransmit data, according to an embodiment.

FIG. 3B illustrates components of a wireless device configured toreceive data, according to an embodiment.

FIG. 4 illustrates Inter-Frame Space (IFS) relationships.

FIG. 5 illustrates a Carrier Sense Multiple Access/Collision Avoidance(CSMA/CA) based frame transmission procedure.

FIG. 6A illustrates a High Efficiency (HE) PHY Protocol Data Units(PPDU), according to an embodiment.

FIG. 6B shows a Table 1 disclosing additional properties of fields ofthe HE PPDU frame of FIG. 6A, according to an embodiment.

FIG. 7A illustrates a format of a High Efficiency (HE) Single User (SU)PPDU according to an embodiment.

FIG. 7B illustrates a format of an HE Multi-User (MU) PPDU frameaccording to an embodiment.

FIG. 7C illustrates a format of an HE Extended Range (ER) SU PPDUaccording to an embodiment.

FIG. 7D illustrates a format of an HE Trigger-Based (TB) PPDU 700Daccording to an embodiment.

FIG. 8 illustrates a Trigger frame according to an embodiment.

FIG. 9 illustrates a Common Info field according to an embodiment.

FIG. 10 illustrates a User Info field according to an embodiment.

FIG. 11 illustrates a PPDU used when the Doppler subfield is set to 1,according to an embodiment.

FIG. 12 illustrates signaling of a PPDU format according to anembodiment.

FIG. 13 illustrates a process, according to an embodiment, fordetermining a mid-amble periodicity M according to format of a PPDU.

FIG. 14 illustrates a process, according to another embodiment, fordetermining a mid-amble periodicity M according to format of a PPDU.

FIG. 15 illustrates a process, according to another embodiment, fordetermining a mid-amble periodicity M according to format of a PPDU.

FIG. 16 illustrates a process, according to another embodiment, fordetermining a mid-amble periodicity M according to format of a PPDU.

FIG. 17 illustrates a PPDU including mid-ambles according to anembodiment.

FIG. 18 illustrates a PPDU including mid-ambles according to anembodiment.

FIG. 19 illustrates features of a PPDU including mid-ambles according toanother embodiment.

FIG. 20 illustrates a PPDU including mid-ambles according to anotherembodiment.

FIG. 21 illustrates a process, according to an embodiment, for receivinga PPDU having a data field that includes mid-ambles.

FIG. 22 illustrates a process, according to an embodiment, for receivinga data field of a PPDU including mid-ambles.

DETAILED DESCRIPTION

The technology described herein relates generally to wirelessnetworking. More particularly, the technology relates to communicationof PHY Protocol Data Units (PPDUs) including data fields wherein thedata field include mid-ambles.

In the following detailed description, certain illustrative embodimentshave been illustrated and described. As those skilled in the art wouldrealize, these embodiments are capable of modification in variousdifferent ways without departing from the scope of the presentdisclosure. Accordingly, the drawings and description are to be regardedas illustrative in nature and not restrictive. Like reference numeralsdesignate like elements in the specification.

FIG. 1 illustrates a wireless network according to an embodiment. Thewireless networks includes an infrastructure Basic Service Set (BSS) 100of a Wireless Local Area Networks (WLAN). In an 802.11 WLAN, the BSSprovides the basic organizational unit and typically includes an AccessPoint (AP) and one or more associated stations (STAs).

The first BSS 100 includes an Access Point 102 (also referred to as AP)wirelessly communicating with first, second, third, and fourth wirelessdevices (or stations) 104, 106, 108, and 110 (also referred to asstations STA1, STA2, STA3, and STA4, respectively). The wireless devicesmay each include a medium access control (MAC) layer and a physical(PHY) layer according to an IEEE 802.11 standard.

Although FIG. 1 shows the first BSS 100 including only the first tofourth stations STA1 to STA4, embodiments are not limited thereto andmay comprise BSSs including any number of stations.

The AP 102 is a station, that is, a STA, configured to control andcoordinate functions of the BSS 100. The AP 102 may transmit informationto a single station selected from the plurality of stations STA1 to STA4in the first BSS 100 using a single frame, or may simultaneouslytransmit information to two or more of the stations STA1 to STA4 in thefirst BSS 100 using either a single Orthogonal Frequency DivisionMultiplexing (OFDM) broadcast frame, a single OFDM Multi-UserMulti-Input-Multi-Output (MU-MIMO) transmission, a single OrthogonalFrequency Division Multiple Access (OFDMA) frame, or a single MU-MIMOOFDMA frame.

The stations STA1 to STA4 may each transmit data to the AP 102 using asingle frame, or transmit information to and receive information fromeach other using a single frame. Two or more of the stations STA1 toSTA4 may simultaneously transmit data to the AP 102 using an Uplink (UL)OFDMA frame, an UL MU-MIMO frame, or an UL MU-MIMO OFDMA frame.

In another embodiment, the AP 102 may be absent and the stations STA1 toSTA4 may be in an ad-hoc network.

FIG. 1 shows a first Down-Link (DL) transmission 114 and a first Up-Link(UL) transmission 112 of the first BSS 100.

Each of the stations STA1 to STA4 and the AP 102 includes a processorand one or more transceiver circuits, and may further include a userinterface and a display device.

The processor is configured to generate a frame to be transmittedthrough a wireless network, to process a frame received through thewireless network, and to execute protocols of the wireless network. Theprocessor may perform some or all of its functions by executing computerprogramming instructions stored on a non-transitory computer-readablemedium.

The transceiver represents a unit functionally connected to theprocessor, and designed to transmit and receive a frame through thewireless network. The transceiver may include a single component thatperforms the functions of transmitting and receiving, or two separatecomponents each performing one of such functions.

The processor and transceiver of the stations STA1 to STA4 and the AP102 may be respectively implemented using hardware components, softwarecomponents, or both.

The first AP 102 may be or include a WLAN router, a stand-alone AccessPoint, a WLAN bridge, a Light-Weight Access Point (LWAP) managed by aWLAN controller, and the like. In addition, a device such as a personalcomputer, tablet computer, or cellular phone may configured to be ableto operate as the AP 102, such as when a cellular phone is configured tooperate as a wireless “hot spot.”

Each of the stations STA1 to STA4 may be or may include a desktopcomputer, a laptop computer, a tablet PC, a wireless phone, a mobilephone, a smart phone, an e-book reader, a Portable Multimedia Player(PMP), a portable game console, a navigation system, a digital camera, aDigital Multimedia Broadcasting (DMB) player, a digital audio recorder,a digital audio player, a digital picture recorder, a digital pictureplayer, a digital video recorder, a digital video player, and the like.

The present disclosure may be applied to WLAN systems according to IEEE802.11 standards but embodiments are not limited thereto.

In IEEE 802.11 standards, frames exchanged between stations (includingaccess points) are classified into management frames, control frames,and data frames. A management frame may be a frame used for exchangingmanagement information that is not forwarded to a higher layer of acommunication protocol stack. A control frame may be a frame used forcontrolling access to a medium. A data frame may be a frame used fortransmitting data to be forwarded to the higher layer of thecommunication protocol stack.

A type and subtype of a frame may be identified using a type fieldand/or a subtype field included in a control field of the frame, asprescribed in the applicable standard.

FIG. 2 illustrates a schematic block diagram of a wireless device 200according to an embodiment. The wireless or WLAN device 200 may beincluded in the AP 102 or any of the stations STA1 to STA4 in FIG. 1.The WLAN device 200 includes a baseband processor 210, a radio frequency(RF) transceiver 240, an antenna unit 250, a storage device (e.g.,memory) 232, one or more input interfaces 234, and one or more outputinterfaces 236. The baseband processor 210, the memory 232, the inputinterfaces 234, the output interfaces 236, and the RF transceiver 240may communicate with each other via a bus 260.

The baseband processor 210 performs baseband signal processing, andincludes a MAC processor 212 and a PHY processor 222. The basebandprocessor 210 may utilize the memory 232, which may include anon-transitory computer readable medium having software (e.g., computerprogramming instructions) and data stored therein.

In an embodiment, the MAC processor 212 includes a MAC softwareprocessing unit 214 and a MAC hardware processing unit 216. The MACsoftware processing unit 214 may implement a first plurality offunctions of the MAC layer by executing MAC software, which may beincluded in the software stored in the memory 232. The MAC hardwareprocessing unit 216 may implement a second plurality of functions of theMAC layer in special-purpose hardware. However, the MAC processor 212 isnot limited thereto. For example, the MAC processor 212 may beconfigured to perform the first and second plurality of functionsentirely in software or entirely in hardware according to animplementation.

The PHY processor 222 includes a transmitting signal processing unit(SPU) 224 and a receiving SPU 226. The PHY processor 222 implements aplurality of functions of the PHY layer. These functions may beperformed in software, hardware, or a combination thereof according toan implementation.

Functions performed by the transmitting SPU 224 may include one or moreof Forward Error Correction (FEC) encoding, stream parsing into one ormore spatial streams, diversity encoding of the spatial streams into aplurality of space-time streams, spatial mapping of the space-timestreams to transmit chains, inverse Fourier Transform (iFT) computation,Cyclic Prefix (CP) insertion to create a Guard Interval (GI), and thelike. Functions performed by the receiving SPU 226 may include inversesof the functions performed by the transmitting SPU 224, such as GIremoval, Fourier Transform computation, and the like.

The RF transceiver 240 includes an RF transmitter 242 and an RF receiver244. The RF transceiver 240 is configured to transmit first informationreceived from the baseband processor 210 to the WLAN, and provide secondinformation received from the WLAN to the baseband processor 210.

The antenna unit 250 includes one or more antennas. When Multiple-InputMultiple-Output (MIMO) or Multi-User MIMO (MU-MIMO) is used, the antennaunit 250 may include a plurality of antennas. In an embodiment, theantennas in the antenna unit 250 may operate as a beam-formed antennaarray. In an embodiment, the antennas in the antenna unit 250 may bedirectional antennas, which may be fixed or steerable.

The input interfaces 234 receive information from a user, and the outputinterfaces 236 output information to the user. The input interfaces 234may include one or more of a keyboard, keypad, mouse, touchscreen,microphone, and the like. The output interfaces 236 may include one ormore of a display device, touch screen, speaker, and the like.

As described herein, many functions of the WLAN device 200 may beimplemented in either hardware or software. Which functions areimplemented in software and which functions are implemented in hardwarewill vary according to constraints imposed on a design. The constraintsmay include one or more of design cost, manufacturing cost, time tomarket, power consumption, available semiconductor technology, and soon.

As described herein, a wide variety of electronic devices, circuits,firmware, software, and combinations thereof may be used to implementthe functions of the components of the WLAN device 200. Furthermore, theWLAN device 200 may include other components, such as applicationprocessors, storage interfaces, clock generator circuits, power supplycircuits, and the like, which have been omitted in the interest ofbrevity.

FIG. 3A illustrates components of a wireless device configured totransmit data according to an embodiment, including a Transmitting (Tx)SPU (TxSP) 324, an RF transmitter 342, and an antenna 352. In anembodiment, the TxSP 324, the RF transmitter 342, and the antenna 352correspond to the transmitting SPU 224, the RF transmitter 242, and anantenna of the antenna unit 250 of FIG. 2, respectively.

The TxSP 324 includes an encoder 300, an interleaver 302, a mapper 304,an inverse Fourier transformer (IFT) 306, and a guard interval (GI)inserter 308.

The encoder 300 receives and encodes input data DATA. In an embodiment,the encoder 300 includes a forward error correction (FEC) encoder. TheFEC encoder may include a binary convolutional code (BCC) encoderfollowed by a puncturing device. The FEC encoder may include alow-density parity-check (LDPC) encoder.

The TxSP 324 may further include a scrambler for scrambling the inputdata before the encoding is performed by the encoder 300 to reduce theprobability of long sequences of 0s or 1s. When the encoder 300 performsthe BCC encoding, the TxSP 324 may further include an encoder parser fordemultiplexing the scrambled bits among a plurality of BCC encoders. IfLDPC encoding is used in the encoder, the TxSP 324 may not use theencoder parser.

The interleaver 302 interleaves the bits of each stream output from theencoder 300 to change an order of bits therein. The interleaver 302 mayapply the interleaving only when the encoder 300 performs the BCCencoding, and otherwise may output the stream output from the encoder300 without changing the order of the bits therein.

The mapper 304 maps the sequence of bits output from the interleaver 302to constellation points. If the encoder 300 performed LDPC encoding, themapper 304 may also perform LDPC tone mapping in addition to theconstellation mapping.

When the TxSP 324 performs a MIMO or MU-MIMO transmission, the TxSP 324may include a plurality of interleavers 302 and a plurality of mappers304 according to a number of spatial streams (NSS) of the transmission.The TxSP 324 may further include a stream parser for dividing the outputof the encoder 300 into blocks and may respectively send the blocks todifferent interleavers 302 or mappers 304. The TxSP 324 may furtherinclude a space-time block code (STBC) encoder for spreading theconstellation points from the spatial streams into a number ofspace-time streams (NSTS) and a spatial mapper for mapping thespace-time streams to transmit chains. The spatial mapper may use directmapping, spatial expansion, or beamforming.

The IFT 306 converts a block of the constellation points output from themapper 304 (or, when MIMO or MU-MIMO is performed, the spatial mapper)to a time domain block (i.e., a symbol) by using an inverse discreteFourier transform (IDFT) or an inverse fast Fourier transform (IFFT). Ifthe STBC encoder and the spatial mapper are used, the IFT 306 may beprovided for each transmit chain.

When the TxSP 324 performs a MIMO or MU-MIMO transmission, the TxSP 324may insert cyclic shift diversities (CSDs) to prevent unintentionalbeamforming. The TxSP 324 may perform the insertion of the CSD before orafter the IFT 306. The CSD may be specified per transmit chain or may bespecified per space-time stream. Alternatively, the CSD may be appliedas a part of the spatial mapper.

When the TxSP 324 performs a MIMO or MU-MIMO transmission, some blocksbefore the spatial mapper may be provided for each user.

The GI inserter 308 prepends a GI to each symbol produced by the IFT306. Each GI may include a Cyclic Prefix (CP) corresponding to arepeated portion of the end of the symbol that the GI precedes. The TxSP324 may optionally perform windowing to smooth edges of each symbolafter inserting the GI.

The RF transmitter 342 converts the symbols into an RF signal andtransmits the RF signal via the antenna 352. When the TxSP 324 performsa MIMO or MU-MIMO transmission, the GI inserter 308 and the RFtransmitter 342 may be provided for each transmit chain.

FIG. 3B illustrates components of a wireless device configured toreceive data according to an embodiment, including a Receiver (Rx) SPU(RxSP) 326, an RF receiver 344, and an antenna 354. In an embodiment,the RxSP 326, RF receiver 344, and antenna 354 may correspond to thereceiving SPU 226, the RF receiver 244, and an antenna of the antennaunit 250 of FIG. 2, respectively.

The RxSP 326 includes a GI remover 318, a Fourier transformer (FT) 316,a demapper 314, a deinterleaver 312, and a decoder 310.

The RF receiver 344 receives an RF signal via the antenna 354 andconverts the RF signal into symbols. The GI remover 318 removes the GIfrom each of the symbols. When the received transmission is a MIMO orMU-MIMO transmission, the RF receiver 344 and the GI remover 318 may beprovided for each receive chain.

The FT 316 converts each symbol (that is, each time domain block) into afrequency domain block of constellation points by using a discreteFourier transform (DFT) or a fast Fourier transform (FFT). The FT 316may be provided for each receive chain.

When the received transmission is the MIMO or MU-MIMO transmission, theRxSP 326 may include a spatial demapper for converting the respectiveoutputs of the FTs 316 of the receiver chains to constellation points ofa plurality of space-time streams, and an STBC decoder for despreadingthe constellation points from the space-time streams into one or morespatial streams.

The demapper 314 demaps the constellation points output from the FT 316or the STBC decoder to bit streams. If the received transmission wasencoded using the LDPC encoding, the demapper 314 may further performLDPC tone demapping before performing the constellation demapping.

The deinterleaver 312 deinterleaves the bits of each stream output fromthe demapper 314. The deinterleaver 312 may perform the deinterleavingonly when the received transmission was encoded using the BCC encoding,and otherwise may output the stream output by the demapper 314 withoutperforming deinterleaving.

When the received transmission is the MIMO or MU-MIMO transmission, theRxSP 326 may use a plurality of demappers 314 and a plurality ofdeinterleavers 312 corresponding to the number of spatial streams of thetransmission. In this case, the RxSP 326 may further include a streamdeparser for combining the streams output from the deinterleavers 312.

The decoder 310 decodes the streams output from the deinterleaver 312 orthe stream deparser. In an embodiment, the decoder 312 includes an FECdecoder. The FEC decoder may include a BCC decoder or an LDPC decoder.

The RxSP 326 may further include a descrambler for descrambling thedecoded data. When the decoder 310 performs the BCC decoding, the RxSP326 may further include an encoder deparser for multiplexing the datadecoded by a plurality of BCC decoders. When the decoder 310 performsthe LDPC decoding, the RxSP 326 may not use the encoder deparser.

Before making a transmission, wireless devices such as wireless device200 will assess the availability of the wireless medium using ClearChannel Assessment (CCA). If the medium is occupied, CCA may determinethat it is busy, while if the medium is available, CCA determines thatit is idle.

The PHY entity for IEEE Std 802.11 is based on Orthogonal FrequencyDivision Multiplexing (OFDM) or Orthogonal Frequency Division MultipleAccess (OFDMA). In either OFDM or OFDMA Physical (PHY) layers, a STA iscapable of transmitting and receiving Physical Layer Protocol Data Units(PPDUs) that are compliant with the mandatory PHY specifications. A PHYspecification defines a set of Modulation and Coding Schemes (MCS) and amaximum number of spatial streams. Some PHY entities define downlink(DL) and uplink (UL) Multi-User (MU) transmissions having a maximumnumber of space-time streams (STS) per user and employing up to apredetermined total number of STSs.

FIG. 4 illustrates Inter-Frame Space (IFS) relationships. FIG. 4illustrates a Short IFS (SIFS), a Point Coordination Function (PCF) IFS(PIFS), a Distributed Coordination Function (DCF) IFS (DIFS), and anArbitration IFSs corresponding to an Access Category (AC) ‘i’ (AIFS[i]).FIG. 4 also illustrates a slot time.

A data frame is used for transmission of data forwarded to a higherlayer. The WLAN device transmits the data frame after performing backoffif a DIFS has elapsed during which DIFS the medium has been idle.

A management frame is used for exchanging management information, whichis not forwarded to the higher layer. Subtype frames of the managementframe include a beacon frame, an association request/response frame, aprobe request/response frame, and an authentication request/responseframe.

A control frame is used for controlling access to the medium. Subtypeframes of the control frame include a request to send (RTS) frame, aclear to send (CTS) frame, and an acknowledgement (ACK) frame.

When the control frame is not a response frame of another frame, theWLAN device transmits the control frame after performing backoff if aDIFS has elapsed during which DIFS the medium has been idle. When thecontrol frame is the response frame of another frame, the WLAN devicetransmits the control frame after a SIFS has elapsed without performingbackoff or checking whether the medium is idle.

A WLAN device that supports a Quality of Service (QoS) functionality(that is, a QoS station) may transmit the frame after performing backoffif an AIFS for an associated access category (AC), (AIFS[AC]), haselapsed. When transmitted by the QoS station, any of the data frame, themanagement frame, and the control frame which is not the response framemay use the AIFS[AC] of the AC of the transmitted frame.

A WLAN device may perform a backoff procedure when the WLAN device thatis ready to transfer a frame finds the medium busy. In addition, a WLANdevice operating according to the IEEE 802.11n and 802.11ac standardsmay perform the backoff procedure when the WLAN device infers that atransmission of a frame by the WLAN device has failed.

The backoff procedure includes determining a random backoff timecomposed of N backoff slots, each backoff slot having a duration equalto a slot time and N being an integer number greater than or equal tozero. The backoff time may be determined according to a length of aContention Window (CW). In an embodiment, the backoff time may bedetermined according to an AC of the frame. All backoff slots occurfollowing a DIFS or Extended IFS (EIFS) period during which the mediumis determined to be idle for the duration of the period.

When the WLAN device detects no medium activity for the duration of aparticular backoff slot, the backoff procedure shall decrement thebackoff time by the slot time. When the WLAN determines that the mediumis busy during a backoff slot, the backoff procedure is suspended untilthe medium is again determined to be idle for the duration of a DIFS orEIFS period. The WLAN device may perform transmission or retransmissionof the frame when the backoff timer reaches zero.

The backoff procedure operates so that when multiple WLAN devices aredeferring and execute the backoff procedure, each WLAN device may selecta backoff time using a random function, and the WLAN device selectingthe smallest backoff time may win the contention, reducing theprobability of a collision.

FIG. 5 illustrates a Carrier Sense Multiple Access/Collision Avoidance(CSMA/CA) based frame transmission procedure for avoiding collisionbetween frames in a channel according to an embodiment. FIG. 5 shows afirst station STA1 transmitting data, a second station STA2 receivingthe data, and a third station STA3 that may be located in an area wherea frame transmitted from the STA1, a frame transmitted from the secondstation STA2, or both can be received. The stations STA1, STA2, and STA3may be WLAN devices.

The STA1 may determine whether the channel is busy by carrier sensing.The STA1 may determine the channel occupation based on an energy levelin the channel or an autocorrelation of signals in the channel, or maydetermine the channel occupation by using a network allocation vector(NAV) timer.

After determining that the channel is not used by other devices (thatis, that the channel is IDLE) during a DIFS (and performing backoff ifrequired), the STA1 may transmit a Ready-To-Send (RTS) frame to thesecond station STA2. Upon receiving the RTS frame, after a SIFS thesecond station STA2 may transmit a Clear-To-Send (CTS) frame as aresponse of the RTS frame. If Dual-CTS is enabled and the second stationSTA2 is an AP, the AP may send two CTS frames in response to the RTSframe: a first CTS frame in the legacy non-HT format, and a second CTSframe in the HT format.

When the third station STA3 receives the RTS frame, it may set a NAVtimer of the third station STA3 for a transmission duration ofsubsequently transmitted frames (for example, a duration of SIFS+CTSframe duration+SIFS+data frame duration+SIFS+ACK frame duration) usingduration information included in the RTS frame. When the third stationSTA3 receives the CTS frame, it may set the NAV timer of the thirdstation STA3 for a transmission duration of subsequently transmittedframes using duration information included in the CTS frame. Uponreceiving a new frame before the NAV timer expires, the third stationSTA3 may update the NAV timer of the third station STA3 by usingduration information included in the new frame. The third station STA3does not attempt to access the channel until the NAV timer expires.

When the STA1 receives the CTS frame from the second station STA2, itmay transmit a data frame to the second station STA2 after SIFS elapsesfrom a time when the CTS frame has been completely received. Uponsuccessfully receiving the data frame, the second station STA2 maytransmit an ACK frame as a response of the data frame after SIFSelapses.

When the NAV timer expires, the third station STA3 may determine whetherthe channel is busy using the carrier sensing. Upon determining that thechannel is not used by other devices during a DIFS after the NAV timerhas expired, the third station STA3 may attempt to access the channelafter a contention window according to a backoff process elapses.

When Dual-CTS is enabled, a station that has obtained a transmissionopportunity (TXOP) and that has no data to transmit may transmit aCF-End frame to cut short the TXOP. An AP receiving a CF-End framehaving a Basic Service Set Identifier (BSSID) of the AP as a destinationaddress may respond by transmitting two more CF-End frames: a firstCF-End frame using Space Time Block Coding (STBC) and a second CF-Endframe using non-STBC. A station receiving a CF-End frame resets its NAVtimer to 0 at the end of the PPDU containing the CF-End frame.

FIG. 5 shows the second station STA2 transmitting an ACK frame toacknowledge the successful reception of a frame by the recipient.

The PHY entity for IEEE Std 802.11 is based on Orthogonal FrequencyDivision Multiplexing (OFDM) or Orthogonal Frequency Division MultipleAccess (OFDMA). In either OFDM or OFDMA Physical (PHY) layers, a STA iscapable of transmitting and receiving PHY Protocol Data Units (PPDUs)that are compliant with the mandatory PHY specifications.

A PHY entity may provide support for 20 MHz, 40 MHz, 80 MHz, and 160 MHzcontiguous channel widths and support for an 80+80 MHz non-contiguouschannel width. Each channel includes a plurality of subcarriers, whichmay also be referred to as tones.

A PHY entity may define fields denoted as Legacy Signal (L-SIG), SignalA (SIG-A), and Signal B (SIG-B) within which some necessary informationabout PHY Service Data Unit (PSDU) attributes are communicated. Forexample, a High Efficiency (HE) PHY entity may define an L-SIG field, anHE Signal A (HE-SIG-A) field, and an HE Signal B (HE-SIG-B) field.

The descriptions below, for sake of completeness and brevity, refer toOFDM-based 802.11 technology. Unless otherwise indicated, a stationrefers to a non-AP HE STA, and an AP refers to an HE AP.

In the IEEE Std 802.11ac, SIG-A and SIG-B fields are called VHT SIG-Aand VHT SIG-B fields. Hereinafter, IEEE Std 802.11ax SIG-A and SIG-Bfields are respectively referred to as HE-SIG-A and HE-SIG-B fields.

FIG. 6A illustrates an HE PPDU 600 according to an embodiment. Atransmitting station generates the HE PPDU frame 600 and transmits it toone or more receiving stations. The receiving stations receive, detect,and process the HE PPDU frame 600.

The HE PPDU frame 600 includes a Legacy Short Training Field (L-STF)602, a Legacy (i.e., a Non-High Throughput (Non-HT)) Long Training Field(L-LTF) 604, a Legacy Signal (L-SIG) field 606, which together comprisea legacy preamble 601 and a Repeated L-SIG field (RL-SIG) 608. The L-STF604 of the HE PPDU has a periodicity of 0.8 μs with 10 periods.

The HE PPDU frame 600 also includes an HE Signal A (HE-SIG-A) field 610,an HE Signal B (HE-SIG-B) field 612, an HE-STF 614, an HE-LTF 616, andan HE-Data field 618. In an embodiment, the HE PPDU frame 600 includes aplurality of HE-SIG-B fields 612 corresponding to different channels,and respective pluralities of HE-STFs 614, HE-LTFs 616, and HE-Datafields 618 corresponding to different channels or resource units.

The legacy preamble 601, the RL-SIG field 608, the HE-SIG-A field 610,and the HE-SIG-B field 612 when present, comprise a first part of the HEPPDU frame 600. In an embodiment, the first part of the HE PPDU frame600 is decoded using a 64-element Discrete Fourier Transform (DFT),having a basic subcarrier spacing of 312.5 KHz.

The HE-SIG-A field 610 is duplicated on each 20 MHz segment after thelegacy preamble to indicate common control information. The HE-SIG-Afield 610 includes a plurality of OFDM HE-SIG-A symbols 620 each havinga duration (including a Guard Interval (GI)) of 4 μs. A number of theHE-SIG-A symbols 620 in the HE-SIG-A field 610 is determined as either 2or 4 depending on a type of the HE PPDU 600. In an embodiment, anHE-SIG-A field 610 of an HE Extended Range Single User (SU) PPDU include4 HE-SIG-A symbols 620, and HE-SIG-A fields 610 of other types of HEPPDU include 2 HE-SIG-A symbols 620.

The HE-SIG-B field 612 is included in HE Multi-User (MU) PPDU(s). TheHE-SIG-B field 612 includes a plurality of OFDM HE-SIG-B symbols 622each having a duration including a GI of 4 μs. In embodiments, one ormore of HE SU PPDUs, HE Tigger-based PPDUs, and HE Extended Range SUPPDUs do not include the HE-SIG-B field 612. A number of the HE-SIG-Bsymbols 622 in the HE-SIG-B field 612 is indicated by N_(HE-SIGB) in theHE-SIG-A field 610 and is variable.

When the HE PPDU 600 has a bandwidth of 40 MHz or more, the HE-SIG-Bfield 612 may be transmitted in first and second HE-SIG-B channels 1 and2. The HE-SIG-B field in the HE-SIG-B channel 1 is referred to as theHE-SIG-B1 field, and the HE-SIG-B field in the HE-SIG-B channel 2 isreferred to as the HE-SIG-B2 field. The HE-SIG-B1 field and theHE-SIG-B2 field are communicated using different 20 MHz bandwidths ofthe HE PPDU 600, and may contain different information. Within thisdocument, the term “HE-SIG-B field” may refer to an HE-SIG-B field of a20 MHz PPDU, or to either or both of an HE-SIG-B1 field or HE-SIG-B2field of a 40 MHz or more PPDU.

An HE-STF 614 of a non-trigger-based PPDU has a periodicity of 0.8 μswith 5 periods. A non-trigger-based PPDU is a PPDU that is not sent inresponse to a trigger frame. An HE-STF 614 of a trigger-based PPDU has aperiodicity of 1.6 μs with 5 periods. Trigger-based PPDUs include ULPPDUs sent in response to respective trigger frames.

The HE-LTF 616 includes one or more OFDM HE-LTF symbols 626 each havinga duration of 12.8 μs plus a Guard Interval (GI). The HE PPDU frame 600may support a 2×LTF mode and a 4×LTF mode. In the 2×LTF mode, an HE-LTFsymbol 626 excluding a Guard Interval (GI) is equivalent to modulatingevery other tone in an OFDM symbol of 12.8 μs excluding the GI, and thenremoving the second half of the OFDM symbol in a time domain. A numberof the HE-LTF symbols 626 in the HE-LTF field 616 is indicated byN_(HE-LTF), and is equal to 1, 2, 4, 6, or 8.

The HE-Data field 618 includes one or more OFDM HE-Data symbols 628 eachhaving a duration of 12.8 μs plus a Guard Interval (GI). A number of theHE-Data symbols 628 in the HE-Data field 618 is indicated by N_(DATA)and is variable.

FIG. 6B shows a Table 1 indicating additional properties of the fieldsof the HE PPDU frame 600 of FIG. 6A, according to an embodiment.

The descriptions below, for sake of completeness and brevity, refer toOFDMA-based 802.11 technology. Unless otherwise indicated, a stationrefers to a non-AP HE STA, and an AP refers to an HE AP.

In this disclosure, multi-user (MU) transmission refers to cases thatmultiple frames are transmitted to or from multiple STAs simultaneouslyusing different resources, wherein examples of different resources aredifferent frequency resources in OFDMA transmission and differentspatial streams in MU-MIMO transmission. Therefore, DL-OFDMA,DL-MU-MIMO, UL-OFDMA, and UL-MU-MIMO are examples of MU transmission.

For several reasons, the IEEE Std 802.11ax may require more protectionmechanisms for MU transmission than the DL MU-MIMO defined in the IEEEStd 802.11ac. The first reason is that the IEEE Std 802.11ax operationscenario is different, in that it encompasses denser wirelessenvironments and outdoor support. Also, the coverage of an IEEE Std802.11ax BSS may be physically larger compared to an IEEE Std 802.11acBSS. Both of these factors create a need for more robust protectionmechanisms.

The second reason is that IEEE Std 802.11ax supports not only DL MUtransmission but also UL MU transmission. In the case of UL MUtransmission, as the number of frames that might be transmitted fromeach STA are larger, it requires more protection from other nearbytransmitting STAs. Another reason is that in an IEEE Std 802.11axenvironment, an AP may want to have more control of the medium by use ofscheduled access mechanisms, which may involve more frequent use ofOFDMA/MU-MIMO transmissions.

UL MU PPDUs (MU-MIMO or OFDMA) are sent as a response to a Trigger framesent by the AP. The Trigger frame may have enough STA specificinformation and respective assigned resource units to identify the STAswhich are supposed to transmit UL MU PPDUs.

Four HE PPDU formats, illustrated in FIGS. 7A through 7D, are defined bythe IEEE Std 802.11ax: HE SU PPDU, HE MU PPDU, HE extended range SU PPDUand HE trigger-based (TB) PPDU. Elements in FIGS. 7A through 7D havingreference characters of the form 7xx are substantially similar toelements of FIG. 6A having reference characters of the form 6xx, anddescriptions thereof are therefore omitted for brevity. The frames shownin FIGS. 7A through 7D also include a Packet Extension (PE) 730.

FIG. 7A illustrates a format of a High Efficiency (HE) Single User (SU)PPDU 700A according to an embodiment. The HE SU PPDU 700A is used for SUtransmission and in this format the HE-SIG-A field 710 is not repeated.The HE SU PPDU 700A does not have an HE-SIG-B field.

FIG. 7B illustrates a format of an HE Multi-User (MU) PPDU frame 700Baccording to an embodiment. This format is used for MU transmissionsthat are not a response of a Trigger frame. An HE-SIG-B field 712 ispresent in this format. A number of symbols in the HE-SIG-B field 712may be determined according to information in the HE-SIG-A field 710(for example, an HE-SIG-B compression indication), a bandwidth of thePPDU frame 700B, and a number of User fields indicated in a Common fieldof the HE-SIG-B field 712 when the Common field is present in theHE-SIG-B field 712.

FIG. 7C illustrates a format of an HE Extended Range (ER) SU PPDU 700Caccording to an embodiment. This format is used for SU transmission andin this format the HE-SIG-A field 710 is repeated (as first and secondHE-SIG-A field 710-1 and 710-2).

FIG. 7D illustrates a format of an HE Trigger-Based (TB) PPDU 700Daccording to an embodiment.

FIG. 8 illustrates a Trigger frame 800 according to an embodiment. TheTrigger frame 800 is used to allocate resources for a UL MU transmissionand to solicit the UL MU transmission to be performed after (as aresponse to) the PPDU that carries the Trigger frame. The Trigger framealso carries other information required by the responding STAs to sendthe UL MU transmission.

The Trigger frame 800 includes a Frame Control field 802, a Durationfield 804, a Receiver Address (RA) field 806, a Transmitter Address (TA)field 808, a Common Info field 810, on or more User Info fields 812-x,optional Padding 814, and a Frame Check Sequence (FCS) field 816.

A value of the Frame Control field 802 indicates that the Trigger frame800 is a trigger frame. A value of the Duration field 804 indicates alength of the Trigger frame 800. A value of the RA field 806 of theTrigger frame is the address of a recipient station or a broadcastaddress corresponding to one or more recipient stations. A value of a TAfield 804 of the Trigger frame is an address of the station transmittingthe Trigger frame.

FIG. 9 illustrates a Common Info field 910 according to an embodiment.The Common info field 910 is suitable for use as the Common info field810 of the Trigger frame 800 of FIG. 8. The Common Info field 910includes a Trigger Type subfield 922, a Length subfield 924, a CascadeInformation subfield 926, a Carrier Sense (CS) Required subfield 928, aBandwidth (BW) subfield 930, a Guard Interval (GI) and Long TrainingField (LTF) Type subfield 932, a Number of HE-LTF Symbols subfield 936,a Space-Time Bloc Coding subfield 938, a Spatial Reuse subfield 946, aDoppler subfield 948, and a HE-SIG-A Reserved subfield 950. In someTrigger frames, the Common Info field 910 also includes aTrigger-Dependent Common Info subfield 954.

The Trigger Type subfield 922 that indicates a type of the Triggerframe. Depending on the type of the Trigger frame, the Trigger frame caninclude the optional type-specific Trigger Dependent Common Info field954 and (in each of the Per User Info field(s) of the Trigger frame)optional Type-specific Per User Info fields.

The Length subfield 924 that indicates the value of an L-SIG Lengthfield of an HE TB PPDU transmitted in response to the Trigger frame. TheCascade Indication subfield 926 when set to 1 indicates that asubsequent Trigger frame follows the current Trigger frame, and thatotherwise has a value of 0.

The CS Required subfield 928 being set to 1 indicates that station(s)identified in the Per User Info field(s) of the Trigger frame arerequired to use Energy Detect (ED) to sense the medium and to considerthe medium state and a NAV in determining whether to respond to theTrigger frame. The CS Required subfield 928 being set to 0 indicatesthat the station(s) identified in the Per User Info field(s) are notrequired to consider the medium state or the NAV in determining whetherto respond to the Trigger frame.

The BW subfield 930 indicates a bandwidth in an HE-SIG-A field of an HETB PPDU transmitted in response to the Trigger Frame. The CP and LTFType subfield 932 indicates a CP and an HE-LTF type of the HE TB PPDUtransmitted in response to the Trigger frame.

The HE-SIG-A Reserved subfield 950 indicates contents of an HE-SIG-Afield of the HE TB PPDU transmitted in response to the Trigger frame. Inan embodiment, all values in the HE-SIG-A Reserved subfield are set to1.

A Spatial Reuse (SR) subfield 946 provides spatial reuse information.For a communication using a 20 MHz BW the SR subfield 946 provides oneSR field corresponding to entire 20 MHz, and the other 3 fields indicateidentical values. For a communication using a 40 MHz BW the SR subfield946 provides two SR field respectively corresponding to each 20 MHz, andthe other 2 fields indicate identical values. For a communication usingan 80 MHz BW the SR subfield 946 provides four SR field respectivelycorresponding to each 20 MHz. For a communication using a 160 MHz BW theSR subfield 946 provides four SR field respectively corresponding toeach 40 MHz.

The Doppler subfield 948 supports proper performance even in outdoormobility use cases. When the Doppler subfield 948 indicates a firstvalue (e.g., is set to 1), a PPDU transmitted in response to the Triggerframe including the Common Info field 90 includes Mid-amble fields madeup of multiple HE-LTFs that are inserted every mid-amble periodicity (M)data symbols, as described below.

In some embodiments of the present disclosure, the Common Info field 910may include a Mid-amble Interval (M) field 952, described below,indicating a number of data symbols between mid-ambles when the Dopplersubfield 948 has a value of 1.

FIG. 10 illustrates a User Info field 1012 according to an embodiment.The User Info field 1012 is suitable for use as any or all of the UserInfo fields 812-x of the Trigger frame 800 of FIG. 8. The User Infofield 1012 includes an 12-bit User Identifier indicating an AssociationID (AID12) subfield 1020, a Resource Unit (RU) Allocation subfield 1022,a Coding Type subfield 1024, an MCS subfield 1026, a Dual CarrierModulation (DCM) subfield 1028, and a Spatial Stream (SS) Allocationsubfield 1030. In some Trigger frames, the User Info field 1012 mayinclude a Trigger-Dependent User Info subfield 1036.

A User Identifier (AID12) subfield 1020 indicates an AssociationIdentifier (AID) of a station allocated a Resource Unit (RU) in which totransmit one or more MPDU(s) in the HE TB PPDU transmitted in responseto the Trigger frame. The RU Allocation subfield 1022 indicating the RUto be used to transmit the HE TB PPDU of the station identified by UserIdentifier subfield. A first bit of the RU Allocation subfield 1022 mayindicate whether the allocated RU is located in a primary or anon-primary 80 MHz. The mapping of the subsequent seven bits indices ofthe RU Allocation subfield 1022 to the RU allocation as one of RUaccording to the IEEE Std 802.11ax OFDMA numerology.

The Coding Type subfield 1024 indicates a coding type of the HE TB PPDUtransmitted in response to the Trigger frame of the station identifiedby the User Identifier subfield 1020, and set to 0 for BCC and to 1 forLDPC. The MCS subfield 1026 indicates an MCS of the HE TB PPDUtransmitted in response to the Trigger frame by the station identifiedby User Identifier field.

The Dual Carrier Modulation (DCM) subfield 1028 indicates dual carriermodulation of the HE TB PPDU transmitted in response to the Triggerframe by the station identified by User Identifier field 1020. A valueof 1 indicates that the HE TB PPDU shall use DCM, and a value of 0indicates that it shall not.

The Spatial Stream (SS) Allocation subfield 1030 indicates spatialstreams of the HE TB PPDU transmitted in response to the Trigger frameby the station identified by User Identifier field 1020.

FIG. 11 illustrates a PPDU 1100 used when the Doppler subfield 948 isset to 1, according to an embodiment. In the PPDU format 1100, mid-amblefields made up of one or more HE-LTFs 1106 _(M) inserted every mid-ambleperiodicity (M) data symbols of the transmission, as described below.The number of HE-LTFs 1106 _(M) in each mid-amble field is equal to thenumber of HE-LTFs 1106 _(P) in the preamble of the PPDU wherein HE-LTFs1106 _(M) and HE-LTFs 1106 _(P) are defined as mid-amble HE-LTFs andpreamble HE-LTFs, respectively.

The PPDU 1100 includes a first part 1102 corresponding to the first partof the PPDU 600 of FIG. 6. The first part 1102 is followed by an HE-STF1104 and one or more preamble HE-LTFs 1106 _(P). The first part 1102,HE-STF 1104, and one or more preamble HE-LTFs 1106 _(P) correspond to apreamble of the PPDU 1100.

After the preamble, the PPDU 1100 includes a first data portion 1108-1including M data symbols. After the first data portion 1108-1, the PPDU1100 includes a first mid-amble including one or more mid-amble HE-LTFs1106 _(M). The duration of the first mid-amble is a mid-amble durationT_(MA).

After the first mid-amble, the PPDU 1100 includes a second data portion1108-2 including M data symbols. After the second data portion 1108-2,the PPDU 1100 includes a second mid-amble including one or moremid-amble HE-LTFs 1106 _(M). The duration of the second mid-amble is themid-amble duration T_(MA).

After the second mid-amble, the PPDU 1100 includes a third data portion1108-3 including the remaining data symbols of the PPDU 1100. After thethird data portion 1108-3, the PPDU 1100 includes a Packet Extension1110.

In some embodiments of the present disclosure, the value of M isdetermined using information in a Common Info field of a Trigger framesoliciting the PPDU.

FIG. 12 illustrates signaling of a PPDU format according to anembodiment. FIG. 12 illustrates first, second, and third PPDUs 1200 a,1200 b, and 1200 c each having a different format. Each PPDU includes atleast an L-SIG field 1202, a repeated L-SIG (RL-SIG) field 1204, atleast first and second HE-SIG-A symbols 1206-1 and 1206-2, and an HE-STF1210. In a device operating according to IEEE Std 802.11ax, the devicemay detect the format of a PPDU based on a value of a Length fieldincluded in the L-SIG field 1202 and the rotated constellation ofinitial symbols of the HE-SIG-A field.

In FIG. 12, symbols having a horizontal bar beneath them are modulatedusing Binary Phase Shift Keying (BPSK). Symbols having a vertical barbeneath them are modulated using Quadrature Binary Phase Shift Keying(QBPSK), that is, rotated BPSK.

If a value of the length field in the L-SIG field 1202 modulo 3 is equalto 1, the detected PPDU is either an HE SU PPDU (bit B0 of the HE-SIG-Afield=1) or an HE Trigger based PPDU (bit B0 of the HE-SIG-A field=0).Accordingly, in FIG. 12, PPDU 1200 a is either an HE SU PPDU or an HE TBPPDU.

If a value of the length field in the L-SIG field 1202 modulo 3 is equalto 2, the PPDU format is either an HE extended range SU PPDU (indicatedby second HE-SIG-A symbols 1206-2 being modulated using QBPSK) or an HEMU PPDU (indicated by second HE-SIG-A symbols 1206-2 being modulatedusing BPSK). Accordingly, in FIG. 12, PPDU 1200 b is an HE extendedrange SU PPDU and includes third and fourth HE-SIG-A symbols 1206-3 and1206-4 modulated using BPSK, and PPDU 1200 a is a HE MU PPDU andincludes an HE-SIG-B field 1208, the HE-SIG-B field 1208 including aplurality of symbols.

Embodiments include processes for inserting mid-ambles into a PPDUaccording to the PPDU format, and processes for determining where themid-ambles are inserted in a PPDU once the PPDU format is detected. Howthe mid-ambles are inserted in an HE PPDU could be different dependingon the format of the PPDU.

Generally, information transmitted using higher data rates (e.g. higherMCS) is more vulnerable to detrimental effect associated with mobilityenvironments. Therefore, introducing mid-amble field according to asmall mid-amble periodicity M when higher MCS rates are used can enablecompensation for phase drift and thereby improving performance.

FIG. 13 illustrates a process 1300, according to an embodiment, fordetermining a mid-amble periodicity M according to format of a PPDU. Theprocess 1300 may be used, for example, when Doppler subfield of a Commoninfo field of a Trigger frame is set to 1. In such a case, the process1300 may be used to determine the mid-amble periodicity M of a PPDUtransmitted in response to the Trigger frame.

At S1302, the process 1300 determines whether the PPDU format is any oneof an HE SU, HE SU ER, or HE UL MU format. For a received PPDU, the PPDUformat may be determined according to one or more of a length in anL-SIG field, a modulation of a second symbol of an HE-SIG-A field, and aB0 bit of the HE-SIG-A field. In response to the PPDU format being an HESU, HE SU ER, or HE UL MU format, at S1302 the process 1300 proceeds toS1312; otherwise, at S1302 the process 1300 proceeds to S1304.

At S1304, the process 1300 determines whether the PPDU format is amulti-user HE DL MU format. For a received PPDU, the PPDU format may bedetermined according to a length in an L-SIG field and a modulation of asecond symbol of an HE-SIG-A field. In response to the PPDU format beinga multi-user HE DL MU format, at S1304 the process 1300 proceeds toS1314; otherwise, at S1304 the process 1300 proceeds to S1306.

At S1306, the process 1300 determines whether the PPDU format is an HETrigger-Based (TB) format for a PPDU. In response to the PPDU formatbeing an HE TB format, at S1306 the process 1300 proceeds to S1316;otherwise, at S1306 the process 1300 exits.

At S1312, the process 1300 determines the mid-amble periodicity Maccording to an MCS of the PPDU, and then exits.

At S1314, the process 1300 determines the mid-amble periodicity Maccording to a highest MCS of the respective MCS values of the STAassigned to participate in the MU PPDU, and then exits.

At S1316, the process 1300 determines the mid-amble periodicity Maccording to an a predetermined value, without regard to the values ofassigned MCS in the Trigger frame that solicits the STAs to perform anUL MU transmission, and then exits.

In an embodiment, the mid-amble periodicity M for Trigger-Based PPDUscould be signaled for all STAs participating in the TB PPDU in a fieldof the Trigger frame soliciting the TB PPDU, as previously describedwith respect to FIG. 9.

Referring to FIG. 9, when the Doppler subfield 948 is set to a firststate (e.g., 1), the mid-amble periodicity (M) subfield 952 has a valuecorresponding to a number of data symbols between mid-ambles. When theDoppler subfield 948 is set to a second state (e.g., 0), the mid-ambleperiodicity (M) subfield 952 is reserved.

FIG. 14 illustrates a process 1400, according to another embodiment, fordetermining a mid-amble periodicity M according to format of a PPDU. Theprocess 1400 may be used, for example, when Doppler subfield of a Commoninfo field of a Trigger frame is set to 1. In such a case, the process1500 may be used to determine the mid-amble periodicity M of a PPDUtransmitted in response to the Trigger frame.

At S1402, the process 1400 determines whether the PPDU format is eitherthe HE SU or HE SU ER format. In response to the PPDU format beingeither the HE SU or HE SU ER format, at S1402 the process 1400 proceedsto S1412; otherwise, at S1402 the process 1400 proceeds to S1404.

At S1404, the process 1400 determines whether the PPDU format is amulti-user HE MU format (either UL or DL). In response to the PPDUformat being a multi-user HE MU format, at S1404 the process 1400proceeds to S1414; otherwise, at S1404 the process 1400 proceeds toS1406.

At S1406, the process 1400 determines whether the PPDU format is an HETB format for a PPDU. In response to the PPDU format being an HE TBformat, at S1406 the process 1400 proceeds to S1416; otherwise, at S1406the process 1400 exits.

At S1412, the process 1400 determines the mid-amble periodicity Maccording to an MCS of the PPDU, and then exits.

At S1414, the process 1400 determines the mid-amble periodicity Maccording to a highest MCS of the respective MCS values of the STAassigned to participate in the MU PPDU, and then exits. At S1414, whenonly one STA is assigned to participate in an MU PPDU (for example, anUL MU PPDU), the process 1400 determines the mid-amble periodicity Maccording to an MCS of the only one STA, and then exits.

At S1416, the process 1400 determines the mid-amble periodicity Maccording to a predetermined value, without regard to the values ofassigned MCS in the Trigger frame that solicits the STAs to perform anUL MU transmission, and then exits.

FIG. 15 illustrates a process 1500, according to another embodiment, fordetermining a mid-amble periodicity M according to format of a PPDU.

At S1502, the process 1500 determines whether the PPDU format is eitherthe HE SU or HE SU ER format. In response to the PPDU format beingeither the HE SU or HE SU ER format, at S1502 the process 1500 proceedsto S1512; otherwise, at S1502 the process 1500 proceeds to S1504.

At S1504, the process 1500 determines whether the PPDU format is amulti-user HE MU format (either UL or DL). In response to the PPDUformat being a multi-user HE MU format, at S1504 the process 1500proceeds to S1516; otherwise, at S1504 the process 1500 proceeds toS1506.

At S1506, the process 1500 determines whether the PPDU format is an HETrigger-Based (TB) format for a PPDU. In response to the PPDU formatbeing an HE TB format, at S1506 the process 1500 proceeds to S1516;otherwise, at S1506 the process 1500 exits.

At S1512, the process 1500 determines the mid-amble periodicity Maccording to an MCS of the PPDU, and then exits.

At S1516, the process 1500 determines the mid-amble periodicity Maccording to a predetermined value, regardless of any MCS values, andthen exits.

FIG. 16 illustrates a process 1600, according to another embodiment, fordetermining a mid-amble periodicity M according to a format of a PPDU.The process 1600 may be used when a Doppler subfield indicates thepresence of mid-ambles in the PPDU.

At S1602, the process 1600 determines whether the PPDU format is a firstformat. In an embodiment, the first format includes the HE SU format. Inan embodiment, the first format includes the HE ER SU format. In anembodiment, the first format includes the single-user HE UL MU format.In response to the PPDU format being the first format, at S1602 theprocess 1600 proceeds to S1612; otherwise, at S1602 the process 1600proceeds to S1604.

At S1604, the process 1600 determines whether the PPDU format is asecond format. In an embodiment, the second format includes the HE MUformat. In an embodiment, the second format includes the HE DL MU formatfor more than one user. In response to the PPDU format being the secondformat, at S1604 the process 1600 proceeds to S1614; otherwise, at S1604the process 1600 proceeds to S1606.

At S1606, the process 1600 determines whether the PPDU format is a thirdformat. In an embodiment, the third format includes the HE TB format. Inan embodiment, the third format includes the HE MU format. In responseto the PPDU format being the third format, at S1606 the process 1600proceeds to S1616; otherwise, at S1606 the process 1600 proceeds toS1608.

At S1608, the process 1600 determines whether the PPDU format is afourth format. In an embodiment, the fourth format includes the HE TBformat. In response to the PPDU format being the fourth format, at S1608the process 1600 proceeds to S1618; otherwise, at S1608 the process 1600exits.

At S1612, the process 1600 determines the mid-amble periodicity Maccording to an MCS of the PPDU, and then exits.

At S1614, the process 1600 determines the mid-amble periodicity Maccording to a highest values of MCS values of all assigned STAs in thePPDU. In an embodiment, only one STA could be assigned. The process 1600then exits.

At S1616, the process 1600 determines the mid-amble periodicity Maccording to a predetermined value, regardless of any MCS values, andthen exits.

At S1618, the process 1600 determines the mid-amble periodicity Maccording to a value indicated in a frame that solicits the STAs to sendthe PPDU in response to the frame, and then exits. In an embodiment, thesoliciting frame could be a Trigger frame.

In a first embodiment, for any of an HE SU PPDU, HE SU extended rangePPDU, and UL HE PPDU for one user transmission, when a Doppler subfieldis set to a first state that indicates that the PPDU is transmitted withmid-ambles, the HE PPDU format is considered in determining themid-amble periodicity M. A transmitter inserts a Mid-amble field afterevery mid-amble periodicity M OFDM data symbols encoded according to anMCS value of the PPDU. Each mid-amble fields may be used to performchannel estimation for data symbols that follow the mid-amble field.When receiving the PPDU, once a receiver decodes an MCS value in a PHYpreamble of the PPDU correctly, the location and length of Mid-amblefield(s) can be determined.

In a DL MU transmission with STAs assigned with different MCS values,the mid-amble fields might not be lined up for the resource blockallocated to the respective STAs, and as a result an FFT window may notline up across resource blocks, which may increase implementationcomplexity. The MCS values for each assigned STA may be determined byall of the all STAs because the HE-SIG-B field that communicates the MCSvalues to the STAs is not beamformed.

In an embodiment, for DL HE MU PPDUs targeted for more than one user,when the Doppler subfield is set to a first state that indicates thatthe PPDU is transmitted with mid-ambles, the HE PPDU format isconsidered in determining the mid-amble periodicity M. A transmitterinserts a Mid-amble field after every mid-amble periodicity M OFDM datasymbol according to a maximum MCS value among the STAs participating inthe DL HE MU PPDU. Each mid-amble fields may be used to perform channelestimation for data symbols that follow the mid-amble field. Whenreceiving the PPDU, once a receiver decodes all the MCS values for eachSTA correctly, the location and length of Mid-amble field(s) can bedetermined based on maximum MCS value among the STAs.

In an UL MU transmission with STAs assigned with different MCS values,the mid-amble fields might not be lined up for the resource blockallocated to the respective STAs, and as a result an FFT window may notline up across resource blocks, which may increase implementationcomplexity. Implementation of an AP may be made easier if all mid-amblefeeds from all users in an UL MU transmission end at a same point.

In an embodiment, for UL HE MU PPDUs, when the Doppler subfield is setto a first state that indicates that the PPDU is transmitted withmid-ambles, the HE PPDU format is considered in determining themid-amble periodicity M for HE trigger-based (TB) PPDUs of the UL HE MUtransmission. Each STA determines all MCS values in each user info fieldof the Trigger frame. A responding STA inserts a Mid-amble field onevery mid-amble periodicity M data symbols based on the maximum MCSvalue among assigned STAs. When the AP receives the HE TB PPDUs from theassigned STAs, the location and length of Mid-amble field can bedetermined according to the maximum MCS value among assigned STAs.

In an embodiment, for UL HE MU PPDUs, when the Doppler subfield of areceived Trigger frame is set to a first state that indicates that thePPDU is transmitted with mid-ambles, the HE PPDU format is considered indetermining the mid-amble periodicity M for HE TB PPDUs transmitted inresponse to the Trigger frame. The mid-amble periodicity M has apredetermined value, and therefore each STA does not need to see all MCSvalues in each user info field of the Trigger frame. A responding STAinserts Mid-amble field after the pre-determined mid-amble periodicity Mdata symbols regardless of MCS values assigned for STAs in ULtransmission. When AP receives the HE TB PPDUs from assigned STAs, thelocation and length of Mid-amble field can be expected based on thepre-determined mid-amble periodicity M value.

FIG. 17 illustrates a PPDU 1700 including mid-ambles according to anembodiment. The PPDU 100 includes a preamble 1702, first, second, andthird data portions 1706-1, 1706-2, and 1706-3, first and secondmid-ambles 1708-1 and 1708-2, and a Packet Extension (PE) 1710. Thefirst data portion 1706-1 starts with a first data symbol 1706S1followed by a second data symbol 1706S2, and ends with a seventh datasymbol 1706S7. The second data portion 1706-2 starts with an eighth datasymbol 1706S8. In the illustrative example shown, the mid-ambleperiodicity M is equal to 7.

A first channel estimation 1722-1 is performed using the preamble 1702to produce parameters for a first equalization 1724-1 to be performed onthe symbols of the first data portion 1706-1. A second channelestimation 1722-2 is performed using the first mid-amble 1708-1 toproduce parameters for a second equalization 1724-2 to be performed onthe symbols of the second data portion 1706-2. A third channelestimation 1722-3 is performed using the second mid-amble 1708-2 toproduce parameters for a third equalization 1724-3 to be performed onthe symbols of the third data portion 1706-3.

For IEEE Std 802.11 devices, a Space-Time Block Coding STBC process hasbeen implemented to provide stable performance in edge areas of an AP'scoverage. STBC operation pairs two OFDM symbols and transmits the pairedsymbols in consecutive time slots, and a receiver decodes the pairedsymbols together. For example, when the PPDU 1700 is transmitted usingSTBC, the first data symbol 1706S1 is paired with the second data symbol1706S2, the third, with the fourth, and so on.

But the paired seventh data symbol 1706S8 and eighth data symbol 1706S8are separated by the first mid-amble 1708-1. As a result, the systemneeds to wait to get the new channel information from the second channelestimation 1722-2 in order to decode the two OFDM symbol together, andneeds to have a two times bigger buffer size in order to store the twodifferent channel information together (here, the results of the firstchannel estimation 1722-1 using the preamble 1702 and the results of thesecond channel estimation 1722-2 using the first mid-amble 1708-1).

In an embodiment, when STBC is enabled and a Doppler subfield is set toa first state to indicate the transmitted PPDU includes one or moremid-amble fields, a transmitter inserts Mid-amble fields after everymid-amble periodicity M OFDM data symbols of a PPDU. If a mid-amblefield is located between two OFDM symbols paired for STBC operation, themid-amble field is shifted to the location after the two paired OFDMsymbols.

In another embodiment, when STBC is enabled and a Doppler subfield isset to a first state to indicate the transmitted PPDU includes one ormore mid-amble fields, a transmitter inserts Mid-amble fields afterevery mid-amble periodicity M OFDM data symbols of a PPDU. If aMid-amble field is located between two OFDM symbols to be paired forSTBC operation the Mid-amble field is shifted to the location before thetwo paired OFDM symbols.

In either embodiment, when receiving the PPDU, once a receiver decodes aSTBC value in the PHY preamble of the PPDU correctly, the location andlength of Mid-amble field can be determined.

In another embodiment, the value of the mid-amble periodicity M isalways an even number, and as a result the Mid-amble field always occursbefore or after two OFDM data symbols paired for STBC operation, andnever occurs between the paired symbols.

When a transmitter sends data of APEP_LENGTH bytes in an HE PPDU whereinthe Doppler subfield is set to the first state (e.g. 1) indicating thepresence of one or more mid-ambles, the data in transmitted in a numberof OFDM data symbols N_(SYM). Depending on the coding scheme, the numberof data symbols N_(SYM), can be determined by:

$\begin{matrix}{{{for}\mspace{14mu}{BCC}\text{:}\mspace{14mu} N_{SYM}} = {m_{STBC} \cdot \left\lceil \frac{\begin{matrix}{{{8 \cdot {APEP}_{-}}{LENGTH}} +} \\{N_{Tail} + N_{Se\tau vice}}\end{matrix}}{m_{STBC}N_{DBPS}} \right\rceil}} & {{Eq}.\mspace{14mu} 1} \\{{{for}\mspace{14mu}{LDPC}\text{:}\mspace{14mu} N_{SYM}} = {m_{STBC} \cdot \left\lceil \frac{\begin{matrix}{{{8 \cdot {APEP}_{-}}{LENGTH}} +} \\N_{Se\tau vice}\end{matrix}}{m_{STBC}N_{DBPS}} \right\rceil}} & {{Eq}.\mspace{14mu} 2}\end{matrix}$wherein m_(STBC) is 2 when STBC is used and 1 otherwise, N_(DBPS) is anumber of data bits per OFDM symbol, N_(Tail) is a number of tail bits(6), and N_(Service) is a number of service bits (16).

Given N_(SYM), the transmitter sets a value of Length field in L-SIG to:

$\begin{matrix}{{Length} = {{\left\lceil \frac{{TXTIME} - {SE} - {20}}{4} \right\rceil \times 3} - 3 - m}} & {{Eq}.\mspace{14mu} 3}\end{matrix}$wherein:TXTIME=20+T _(PA) +N _(SYM) T _(SYM) +N _(MA) T _(MA) +T _(PE) +SE,T _(MA) =N _(HE-LTF) T _(HE-LTF)(+T _(HE-STF)), and

$N_{MA} = \left\{ \begin{matrix}\left\lfloor {N_{SYM}/M} \right\rfloor & {\mspace{14mu}\begin{matrix}{{when}\mspace{14mu}{the}\mspace{14mu}{Doppler}\mspace{14mu}{subfield}} \\{{{indicates}\mspace{14mu}{the}\mspace{14mu}{first}\mspace{14mu}{state}\mspace{14mu}(1)},}\end{matrix}} \\0 & \begin{matrix}{{when}\mspace{14mu}{the}\mspace{14mu}{Doppler}\mspace{14mu}{subfield}} \\{{indicates}\mspace{14mu}{the}\mspace{14mu}{second}\mspace{14mu}{state}\mspace{14mu}{(0).}}\end{matrix}\end{matrix} \right.$when the Doppler subfield indicates the first state (1),when the Doppler subfield indicates the second state (0). and whereinN_(MA) is the number of mid-ambles, M is the mid-amble periodicity, SEis 0 us when the transmission is in a 5 GHz band and is 6 us when thetransmission is in a 2.4 GHz band, T_(PA) is duration of HE preamble asdescribed with respect to FIGS. 7A through 7D, T_(SYM) is duration of aOFDM data symbol, T_(PE) is duration of Packet Extension (which PacketExtensions consists of random values whose average power is that same asthe average power of the OFDM data symbols and secures additionalreceive processing time), and m is 1 for an HE MU PPDU or HE ER SU PPDU,and 2 otherwise. T_(MA) is duration of Mid-amble field, which in anembodiment may include a duration of a HE-STF T_(HE-STF), and in anotherembodiment may not include the duration of a HE-STF T_(HE-STF).

When a receiver receives an HE PPDU, it needs to determine how many OFDMdata symbols, N_(SYM), are transmitted and what amount of time, T_(PE),can be secured for RX processing.

In an embodiment, a device receiving an HE PPDU determines a number ofOFDM symbols used for decoding data symbols of the HE PPDU by finding anumber of OFDM data symbols (N_(SYM)) that satisfies the followingequations:

$\begin{matrix}{\mspace{79mu}{N_{MA} = \left\{ \begin{matrix}\left\lfloor {N_{SYM}/M} \right\rfloor & {\begin{matrix}{{when}\mspace{14mu} a\mspace{14mu}{Doppler}\mspace{14mu}{subfield}} \\{{{indicates}\mspace{14mu} a\mspace{14mu}{mid}\text{-}{amble}\mspace{14mu}{exists}},}\end{matrix}\mspace{14mu}} \\0 & {{otherwise}.}\end{matrix} \right.}} & {{Eq}.\mspace{14mu} 4} \\{N_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - {N_{MA}T_{MA}}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}}}} & {{Eq}.\mspace{14mu} 5}\end{matrix}$wherein b_(PE-Disambiguity) is the value of a PE Disambiguity bit in theHE-SIG-A field of the PPDU. Once N_(SYM) is obtained, T_(PE) iscalculated by:

$\begin{matrix}{T_{PE} = {\left\lfloor \frac{\begin{matrix}{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - {N_{MA}T_{MA}}} \right) -} \\{N_{SYM}T_{SYM}}\end{matrix}}{4} \right\rfloor \times 4}} & {{Eq}.\mspace{14mu} 6}\end{matrix}$

Accordingly, in PPDUs wherein one or more mid-amble fields exist, thereceiver may determine the number of OFDM data symbols N_(SYM) usingEquation 5, but the number of mid-ambles N_(MA) in Equation 5 is afunction of N_(SYM). As a result the number of OFDM symbols N_(SYM)cannot be directly calculated by the receiver, and implementation of thedetermination of the number of OFDM data symbols N_(SYM) in receivedPPDUs including one or more mid-ambles can increase the systemcomplexity compared to the case where a mid-amble field is not includedin the PPDU. Eliminating the circular dependency of Equations 4 and 5 isdifficult because of, for example, the non-linear elements of theequations, such as the floor operations (i.e., └x┘) is each equation.

Embodiments reduce the complexity of a device configured to receive HEPPDUs including mid-ambles by using novel processes for determining thenumber of OFDM symbols N_(SYM) used for data symbols and the PacketExtension duration T_(PE) of the received HE PPDU.

In order to determine the number of OFDM data symbols N_(SYM) at areceiving device, the use of Equation 5 might be considered. ButEquation 5 requires that the value of the number of mid-ambles N_(MA) beknown, and Equation 4 establishes that the number of mid-ambles NA is afunction of the number of OFDM data symbols N_(SYM). Therefore thenumber of OFDM data symbols N_(SYM) cannot be directly calculated usingEquation 5 when a Doppler subfield of an HE-SIG-A field of the PPDUbeing received is set to the first state (e.g. 1), indicating that oneor more mid-ambles are present. Accordingly a new equation and newassumptions are needed to determine N_(SYM). The new equations may bederived as follows:

Step A1) the floor function can be eliminated from Equation 4 byrestating Equation 4 as shown below, using an additional unknownvariable n₀:

for some n₀, 0≤n₀≤M−1,

$\begin{matrix}{N_{MA} = {\left. \frac{N_{SYM} - n_{0}}{M}\Rightarrow N_{SYM} \right. = {{M \cdot N_{MA}} + {n_{0}.}}}} & {{Eq}.\mspace{14mu} 7}\end{matrix}$

Step A2) the floor function can be eliminated from Equation 5 byrestating Equation 5 as shown below using an additional unknown variableα:

for some

$\begin{matrix}{\mspace{79mu}{\alpha,{0 \leq \alpha < 1},}} & \; \\{{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - {N_{MA}T_{MA}}} \right)/T_{SYM}} = {N_{SYM} + b_{{PE}\text{-}{Disambiguity}} + {\alpha.}}} & {{Eq}.\mspace{14mu} 8}\end{matrix}$

Step A3) from Step A1 and Step A2, the following equations can bederived:

$\begin{matrix}{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - {N_{MA}T_{MA}}} \right) = {{T_{SYM}\left( {{M \cdot N_{MA}} + n_{0} + b_{{PE}\text{-}{Disambiguity}} + \alpha} \right)}.}} & {{Eq}.\mspace{14mu} 9} \\{\mspace{79mu}{N_{MA} = \frac{\begin{matrix}{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right) -} \\{T_{SYM}\left( {n_{0} + b_{{PE}\text{-}Disambiguity} + \alpha} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}}}} & {{Eq}.\mspace{14mu} 10}\end{matrix}$

Step A4) from the above, minimum and maximum possible values of n₀ and αmay be used to determine minimum (N_(MA_MIN)) and maximum (N_(MA_MAX))possible values for the number of mid-ambles N_(MA):

$\begin{matrix}{{{{assume}\mspace{14mu}\alpha} = 0},{n_{0} = {{0\text{:}\mspace{14mu} N_{{MA}\_{MAX}}} = \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}b_{{PE}\text{-}{Disambiguity}}}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}}}}} & {{Eq}.\mspace{14mu} 11} \\{{{{assume}\mspace{14mu}\alpha} = 1},{n_{0} = {{M - {1\text{:}\mspace{14mu} N_{{MA}\_{MIN}}}} = \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {b_{{PE}\text{-}Disambiguity} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}}}}} & {{Eq}.\mspace{14mu} 12} \\{\mspace{79mu}{{and}\mspace{14mu}{note}\mspace{14mu}{that}\text{:}}} & \; \\{\mspace{79mu}{N_{{MA}\_{MIN}} < N_{MA} < N_{{MA}\_{MAX}}}} & {{Eq}.\mspace{14mu} 13}\end{matrix}$

Step A5) from the above, determine an equation for(N_(MA_MAX)−N_(MA_MIN)) to determine the scope of the range of possiblevalues for the number of mid-ambles N_(MA):

$\begin{matrix}{{\left( {N_{{MA}\_{MAX}} - N_{{MA}\_{MIN}}} \right) = \frac{M \cdot T_{SYM}}{T_{MA} + {M \cdot T_{SYM}}}},{{{which}\mspace{14mu}{is}} < 1}} & {{Eq}.\mspace{14mu} 14}\end{matrix}$

Because the difference between N_(MA_MAX) and N_(MA_MIN) is less thanone and N_(MA_MAX) is greater than N_(MA_MIN),floor(N_(MA_MAX))=ceiling(N_(MA_MIN)). Relying on this and on the numberof mid-ambles N_(MA) being a positive integer between N_(MA_MAX) andN_(MA_MIN),N _(MA)=floor(N _(MA_MAX))=ceiling(N _(MA_MIN))  Eq. 15

$\begin{matrix}\begin{matrix}{N_{MA} = \left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - {T_{SYM}b_{{PE}\text{-}Disambiguity}}}{T_{MA} + {M \cdot T_{SYM}}} \right\rfloor} \\{= \left\lceil \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {b_{{PE}\text{-}Disambiguity} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rceil}\end{matrix} & {{Eq}.\mspace{14mu} 16}\end{matrix}$Accordingly, using either of the middle or right portions of Equation16, the number of mid-ambles N_(MA) may be determined without firstdetermining the number of OFDM symbols N_(SYM) used for decoding datasymbols (i.e., the number of OFDM data symbols N_(SYM)).

In an embodiment in accordance with Equation 16, a process ofidentifying a number of OFDM data symbols N_(SYM) and a Packet Extensionduration T_(PE) from a received HE PPDU first determines a number ofmid-ambles N_(MA) when the Doppler subfield indicates that mid-amblesare present in the received HE PPDU according to:

$\begin{matrix}{N_{MA} = \left\lfloor \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM} \cdot b_{{PE}\text{-}Disambiguity}}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rfloor} & {{Eq}.\mspace{14mu} 17}\end{matrix}$When the Doppler subfield indicates that mid-ambles are not present inthe HE PPDU, the number of mid-ambles N_(MA) is 0. Unlike a processrelying on Equation 4, the process using Equation 17 to determine thenumber of mid-ambles N_(MA) does not need to first determine the valueN_(SYM) in order to do so.

Once the number of mid-ambles N_(MA) is determined, the process maydetermine the number of OFDM data symbols N_(SYM) according to Equation5 and the Packet Extension duration T_(PE) may be determined accordingto Equation 6.

In another embodiment in accordance with Equation 16, a process ofidentifying a number of OFDM data symbols N_(SYM) and a Packet Extensionduration T_(PE) from a received HE PPDU determines a number ofmid-ambles N_(MA) when the Doppler subfield indicates that mid-amblesare present in an HE PPDU according to:

$\begin{matrix}{N_{MA} = \left\lceil \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {b_{{PE}\text{-}Disambiguity} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rceil} & {{Eq}.\mspace{14mu} 18}\end{matrix}$When the Doppler subfield indicates that mid-ambles are not present inthe HE PPDU, the number of mid-ambles N_(MA) is 0. The process usingEquation 18 to determine the number of mid-ambles N_(MA) does not needto first determine the value of N_(SYM) in order to do so.

Once the number of mid-ambles N_(MA) is determined, the process maydetermine the number of OFDM data symbols N_(SYM) according to Equation5 and the Packet Extension duration T_(PE) may be determined accordingto Equation 6.

The analysis that led to Equations 17 and 18 can be generalized to coverother similar relationships between the number of mid-ambles N_(MA) andthe number of OFDM data symbols N_(SYM).

For example, the relationship of Equation 4 would indicate two 2mid-ambles when the number of OFDM data symbols N_(SYM) is equal totwice the mid-amble periodicity M. This would produce a PPDU as shown inFIG. 18.

FIG. 18 illustrates a PPDU 1800 according to an embodiment. Elements ofFIG. 18 having reference characters of the form 18XX or 18XX-X aresimilar to elements of FIG. 17 having respective reference characters ofthe form 17XX or 17XX-X, and descriptions thereof are omitted forbrevity.

The PPDU 1800 includes 2·M OFDM data symbols, where M is the mid-ambleperiodicity. As a result, a mid-amble 1808-1 is inserted after the firstM OFDM data symbols, and because the embodiment was according toEquation 4, another (unnecessary) mid-amble 1826 was inserted after thelast OFDM data symbol. The mid-amble 1826 is unnecessary because thePacket Extension (PE) 1810 is not an OFDM symbols to be decoded, andtherefore the third channel estimation 1822-3 and third equalization1824-3 are not needed.

In an embodiment, to prevent the insertion of this unnecessarymid-amble, a transmitter determines the number of OFDM data symbolsN_(SYM) used in a HE PPDU according to Equation 1 or Equation 2, asappropriate, and the Length field of the L-SIG of the HE PPDU accordingto Equation 3.

Then, instead of determining the number of mid-ambles N_(MA) accordingto Equation 4 above, the transmitter may determine a number ofmid-ambles N_(MA) according to:

$\begin{matrix}{N_{MA} = \left\{ \begin{matrix}\left\lfloor {\left( {N_{SYM} - 1} \right)/M} \right\rfloor & \begin{matrix}{{when}\mspace{14mu}{Doppler}\mspace{14mu}{subfield}} \\{{{indicates}\mspace{14mu}{mid}\text{-}{amble}\mspace{14mu}{exists}},}\end{matrix} \\0 & {{otherwise}.}\end{matrix} \right.} & {{Eq}.\mspace{14mu} 19}\end{matrix}$

When a receiver receives the HE PPDU, it needs to derive how many OFDMdata symbols N_(SYM), that will be decoded to produce data, are beingtransmitted in the received HE PPDU and what amount of additional time,the Packet Extension duration T_(PE), is being provided for receiveprocessing. Equations for doing so may be derived as follows:

Step B1) the floor function can be eliminated from Equation 19 byrestating Equation 19 as shown below using an additional unknownvariable n₀:

for some

$\begin{matrix}{n_{0},{0 \leq n_{0} \leq {M - 1}},{N_{MA} = {\left. \frac{N_{SYM} - 1 - n_{0}}{M}\Rightarrow N_{SYM} \right. = {{M \cdot N_{MA}} + 1 + {n_{0}.}}}}} & {{Eq}.\mspace{14mu} 20}\end{matrix}$

Step B2) the floor function can be eliminated from Equation 5 byrestating Equation 5 as shown below using an additional unknown variableα:

for some

$\begin{matrix}{\mspace{79mu}{\alpha,{0 \leq \alpha < 1},}} & \; \\{{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - {N_{MA}T_{MA}}} \right)/T_{SYM}} = {N_{SYM} + b_{{PE}\text{-}{Disambiguity}} + {\alpha.}}} & {{Eq}.\mspace{14mu} 21}\end{matrix}$

Step B3) from Step B1 and Step B2, the following equations can bederived:

$\begin{matrix}{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - {N_{MA}T_{MA}}} \right) = {{T_{SYM}\left( {{M \cdot N_{MA}} + 1 + n_{0} + b_{{PE}\text{-}{Disambiguity}} + \alpha} \right)}.}} & {{Eq}.\mspace{14mu} 22} \\{\mspace{79mu}{N_{MA} = \frac{\begin{matrix}{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right) -} \\{T_{SYM}\left( {1 + n_{0} + b_{{PE}\text{-}Disambiguity} + \alpha} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}}}} & {{Eq}.\mspace{14mu} 23}\end{matrix}$

Step B4) from the above, minimum and maximum possible values of no and amay be used to determine minimum (N_(MA_MIN)) and maximum (N_(MA_MAX))possible values for the number of mid-ambles N_(MA):

$\begin{matrix}{{{{assume}\mspace{14mu}\alpha} = 0},{n_{0} = {{0\text{:}\mspace{14mu} N_{MA\_ MAX}} = \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + b_{{PE}\text{-}{Disambiguity}}} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}}}}} & {{Eq}.\mspace{14mu} 24} \\{{{{assume}\mspace{14mu}\alpha} = 1},{n_{0} = {{M - {1\text{:}\mspace{14mu} N_{{MA}\_{MIN}}}} = \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + b_{{PE}\text{-}Disambiguity} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}}}}} & {{Eq}.\mspace{14mu} 25} \\{\mspace{79mu}{{and}\mspace{14mu}{note}\mspace{14mu}{that}\text{:}}} & \; \\{\mspace{79mu}{N_{{MA}\_{MIN}} < N_{MA} < N_{{MA}\_{MAX}}}} & {{Eq}.\mspace{14mu} 26}\end{matrix}$

Step B5) from the above, determine an equation for(N_(MA_MAX)−N_(MA_MIN)) to determine the scope of the range of possiblevalues for the number of mid-ambles N_(MA):

$\begin{matrix}{{\left( {N_{{MA}\_{MAX}} - N_{{MA}\_{MIN}}} \right) = \frac{M \cdot T_{SYM}}{T_{MA} + {M \cdot T_{SYM}}}},{{{which}\mspace{14mu}{is}} < 1}} & {{Eq}.\mspace{14mu} 27}\end{matrix}$

Because the difference between N_(MA_MAX) and N_(MA_MIN) is less thanone and N_(MA_MAX) is greater than N_(MA_MIN),floor(N_(MA_MAX))=ceiling(N_(MA_MIN)). Relying on this and that thenumber of mid-ambles N_(MA) must be a positive integer betweenN_(MA_MAX) and N_(MA_MIN),

$\begin{matrix}{N_{MA} = {{{floor}\mspace{14mu}\left( N_{{MA}\_{MAX}} \right)} = {{ceiling}\mspace{14mu}\left( N_{{MA}\_{MIN}} \right)}}} & {{Eq}.\mspace{14mu} 28} \\\begin{matrix}{N_{MA} = \left\lfloor \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + b_{{PE}\text{-}Disambiguity}} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rfloor} \\{= \left\lceil \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + b_{{PE}\text{-}Disambiguity} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rceil}\end{matrix} & {{Eq}.\mspace{14mu} 29}\end{matrix}$Accordingly, the number of mid-ambles N_(MA) may be determined withoutfirst determining the number of OFDM data symbols N_(SYM) using eitherthe middle or right portion of Equation 29.

In an embodiment in accordance with Equation 29, a process ofidentifying a number of OFDM data symbols N_(SYM) and a Packet Extensionduration T_(PE) from a received HE PPDU first determines a number ofmid-ambles N_(MA) when the Doppler subfield indicates that mid-amblesare present in an HE PPDU according to:

$\begin{matrix}{N_{MA} = \left\lfloor \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + b_{{PE}\text{-}Disambiguity}} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rfloor} & {{Eq}.\mspace{14mu} 30}\end{matrix}$When the Doppler subfield indicates that mid-ambles are not present inthe HE PPDU, the number of mid-ambles N_(MA) is 0. Unlike a processrelying on Equation 4, the process using Equation 30 to determine thenumber of mid-ambles NA does not need to first determine the valueN_(SYM) in order to do so.

Once the number of mid-ambles N_(MA) is determined, the process maydetermine the number of OFDM data symbols N_(SYM) according to Equation5 and the Packet Extension duration T_(PE) determined according toEquation 6.

In another embodiment in accordance with Equation 29, a process ofidentifying a number of OFDM data symbols N_(SYM) and a Packet Extensionduration T_(PE) from a received HE PPDU determines a number ofmid-ambles N_(MA) when the Doppler subfield indicates that mid-amblesare present in an HE PPDU according to:

$\begin{matrix}{N_{MA} = \left\lceil \frac{\begin{matrix}{{\frac{{L_{-}{LENGTH}} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + b_{{PE}\text{-}Disambiguity} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rceil} & {{Eq}.\mspace{14mu} 31}\end{matrix}$When the Doppler subfield indicates that mid-ambles are not present inthe HE PPDU, the number of mid-ambles N_(MA) is 0. The process usingEquation 31 to determine the number of mid-ambles N_(MA) does not needto first determine the value of N_(SYM) in order to do so.

Once the number of mid-ambles N_(MA) is determined, the process maydetermine the number of OFDM data symbols N_(SYM) according to Equation5 and the Packet Extension duration T_(PE) determined according toEquation 6.

Generalizing from FIG. 18, FIG. 20 illustrates a PPDU 2000 according toan embodiment. Elements of FIG. 20 having reference characters of theform 20XX or 20XX-X are similar to elements of FIG. 17 having respectivereference characters of the form 17XX or 17XX-X, and descriptionsthereof are omitted for brevity.

The illustrative PPDU 2000 includes 2M+β/OFDM data symbols, where M isthe mid-amble periodicity. In the example shown, β=1. As a result, amid-amble 2008-1 is inserted after the first M OFDM data symbols, andbecause the embodiment was according to Equation 4 (or Equation 19),another (unnecessary) mid-amble 2026 before the last OFDM data symbol2006-2M+1 and the PE 2010. The mid-amble 2026 is unnecessary because theequalization necessary to decode the last OFDM data symbol 2006-2M+1 isprobably substantially the same as the equalization needed to receivethe second-to-the-last OFDM data symbol 2006-2M and the Packet Extension(PE) 2010 is not an OFDM symbols to be decoded. Therefore, the thirdchannel estimation 2022-3 and third equalization 2024-3 are not needed,which means the unnecessary mid-amble 2026 is not needed.

In an embodiment, to prevent the insertion of the unnecessary mid-amble2026, a transmitter determines the number of OFDM symbols N_(SYM) usedfor encoding data symbols in a HE PPDU according to Equation 1 orEquation 2, as appropriate, and the Length field of the L-SIG of the HEPPDU according to Equation 3.

Then, instead of determining the number of mid-ambles N_(MA) accordingto Equations 4 or 19, above, the transmitter may determine a number ofmid-ambles N_(MA) according to:

$\begin{matrix}{N_{MA} = \left\{ \begin{matrix}\left\lfloor {\left( {N_{SYM} - \beta - 1} \right)/M} \right\rfloor & {\begin{matrix}{{when}\mspace{14mu}{Doppler}\mspace{14mu}{subfield}} \\{{{indicates}\mspace{14mu}{mid}\text{-}{ambles}},}\end{matrix}\mspace{14mu}} \\0 & {{otherwise}.}\end{matrix} \right.} & {{{Eq}.\mspace{14mu} 19}A}\end{matrix}$thereby preventing the insertion of another mid-amble when only M+β OFDMdata symbols remain to be transmitted, 0≤β<M after a last mid-amble. Inan embodiment, β=1. Equivalently, because for any positive integers yand z, [y/z]≡┌(y+1)/z┐−1, Equation 19A is equivalent to:

$\begin{matrix}{N_{MA} = \left\{ \begin{matrix}{\left\lceil {\left( {N_{SYM} - \beta} \right)/M} \right\rceil - 1} & {\begin{matrix}{{when}\mspace{14mu}{Doppler}\mspace{14mu}{subfield}} \\{{{indicates}\mspace{14mu}{mid}\text{-}{ambles}},}\end{matrix}\mspace{14mu}} \\0 & {{otherwise}.}\end{matrix} \right.} & {{{Eq}.\mspace{14mu} 19}B}\end{matrix}$

When a receiver receives the HE PPDU, it needs to derive how many OFDMdata symbols, N_(SYM), are being transmitted in the HE-PPDU and whatamount of additional time, the PE duration T_(PE), has been provided forreceive processing. Equations for doing so may be derived as follows:

Step C1) the ceiling function can be eliminated from Equation 19B byrestating Equation 19B as shown below using an additional unknownvariable n₀:

for some

$\begin{matrix}{\mspace{79mu}{n_{0},{0 \leq n_{0} \leq {M - 1}},}} & \; \\{N_{MA} = {\left. {\frac{N_{SYM} - \beta + n_{0}}{M} - 1}\Rightarrow N_{SYM} \right. = {{M \cdot N_{MA}} + M + \beta - {n_{0}.}}}} & {{{Eq}.\mspace{14mu} 20}B}\end{matrix}$

Step C2) the floor function can be eliminated from Equation 5 byrestating Equation 5 as shown below using an additional unknown variableα:

for some

$\begin{matrix}{\mspace{79mu}{\alpha,{0 \leq \alpha < 1},}} & \; \\{{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - {N_{MA}T_{MA}}} \right)/T_{SYM}} = {N_{SYM} + b_{{PE}\text{-}{Disambiguity}} + {\alpha.}}} & {{{Eq}.\mspace{14mu} 21}B}\end{matrix}$

Step C3) from Step C1 and Step C2, the following equations can bederived:

$\begin{matrix}{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - {N_{MA}T_{MA}}} \right) = {{T_{SYM}\left( {{M \cdot N_{MA}} + M + \beta - n_{0} + b_{{PE}\text{-}{Disambiguity}} + \alpha} \right)}.}} & {{{Eq}.\mspace{14mu} 22}B} \\{\mspace{79mu}{N_{MA} = \frac{\begin{matrix}{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right) -} \\{T_{SYM}\left( {M + \beta - n_{0} + b_{{PE}\text{-}Disambiguity} + \alpha} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}}}} & {{{Eq}.\mspace{14mu} 23}B}\end{matrix}$

Step C4) from the above, minimum and maximum possible values of no and amay be used to determine minimum (N_(MA_MIN)) and maximum (N_(MA_MAX))possible values for the number of mid-ambles N_(MA):

$\begin{matrix}{{{{assume}\mspace{14mu}\alpha} = 1},{n_{0} = {{M - {1\text{:}\mspace{20mu} N_{MA_{-}MAX}}} = \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}Disambiguity}} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}}}}} & {{{Eq}.\mspace{14mu} 24}B} \\{{{{assume}\mspace{14mu}\alpha} = 0},{n_{0} = {{0\text{:}\mspace{20mu} N_{MA_{-}{MIN}}} = \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + b_{{PE}\text{-}Disambiguity} + \beta + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}}}}} & {{{Eq}.\mspace{14mu} 25}B}\end{matrix}$and note that:N _(MA_MIN) <N _(MA) <N _(MA_MAX)  Eq. 26B

Step C5) from the above, determine an equation for(N_(MA_MAX)−N_(MA_MIN)) to determine the scope of the range of possiblevalues for the number of mid-ambles N_(MA):

$\begin{matrix}{{\left( {N_{MA_{-}MAX} - N_{MA_{-}{MIN}}} \right) = \frac{M \cdot T_{SYM}}{T_{MA} + {M \cdot T_{SYM}}}},{{{which}\mspace{14mu}{is}} < 1}} & {{{Eq}.\mspace{14mu} 27}B}\end{matrix}$

Because the difference between N_(MA_MAX) and N_(MA_MIN) is less thanone and N_(MA_MAX) is greater than N_(MA_MIN),floor(N_(MA_MAX))=ceiling(N_(MA_MIN)). Relying on this and that thenumber of mid-ambles N_(MA) must be a positive integer betweenN_(MA_MAX) and N_(MA_MIN),

$\begin{matrix}{\mspace{79mu}{N_{MA} = {{{floor}\mspace{14mu}\left( N_{{MA}\_{MAX}} \right)} = {{ceiling}\mspace{14mu}\left( N_{{MA}_{-}MIN} \right)}}}} & {{{Eq}.\mspace{14mu} 28}B} \\{N_{MA} = {\left\lfloor \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}Disambiguity}} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rfloor = \left\lceil \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}Disambiguity} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rceil}} & {{{Eq}.\mspace{14mu} 29}B}\end{matrix}$Accordingly, the number of mid-ambles N_(MA) may be determined withoutfirst determining the number of OFDM data symbols N_(SYM).

In an embodiment in accordance with Equation 29B, a process ofidentifying a number of OFDM data symbols N_(SYM) and a Packet Extensionduration T_(PE) from a HE PPDU being received first determines a numberof mid-ambles NA when the Doppler subfield indicates that mid-ambles arepresent in an HE PPDU according to:

$\begin{matrix}{N_{MA} = \left\lfloor \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}Disambiguity}} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rfloor} & {{{Eq}.\mspace{14mu} 30}B}\end{matrix}$When the Doppler subfield indicates that mid-ambles are not present inthe HE PPDU, the number of mid-ambles N_(MA) is 0. Unlike a processrelying on Equation 4, the process using Equation 30B to determine thenumber of mid-ambles N_(MA) does not need to first determine the valueof N_(SYM) in order to do so.

Once the number of mid-ambles N_(MA) is determined, the process maydetermine the number of OFDM data symbols N_(SYM) according to Equation5 and the Packet Extension duration T_(PE) may be determined accordingto Equation 6.

In another embodiment in accordance with Equation 29B, a process ofidentifying a number of OFDM data symbols N_(SYM) and a Packet Extensionduration T_(PE) from a received HE PPDU determines a number ofmid-ambles N_(MA) when the Doppler subfield indicates that mid-amblesare present in an HE PPDU according to:

$\begin{matrix}{N_{MA} = \left\lceil \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}Disambiguity} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rceil} & {{{Eq}.\mspace{14mu} 31}B}\end{matrix}$When the Doppler subfield indicates that mid-ambles are not present inthe HE PPDU, the number of mid-ambles N_(MA) is 0. The process usingEquation 31B to determine the number of mid-ambles N_(MA) does not needto first determine the value of N_(SYM) in order to do so.

Once the number of mid-ambles N_(MA) is determined, the process maydetermine the number of OFDM data symbols N_(SYM) according to Equation5 and the Packet Extension duration T_(PE) may be determined accordingto Equation 6.

For example, given β=0, each number of mid-ambles N_(MA) from Eq.1, Eq.3and Eq.4 provides exactly the same value at the TX side. Equations 19and 19B generate the same value for the number of mid-ambles N_(MA) atthe receive side.

For another example, given β=1, at the TX side, substituting in 1 for 0in Equation 19B gives:

$\begin{matrix}{N_{MA} = \left\{ \begin{matrix}{\left\lceil {\left( {N_{SYM} - 1} \right)/M} \right\rceil - 1} & {\begin{matrix}{{when}\mspace{14mu}{Doppler}\mspace{14mu}{subfield}} \\{{{indicates}\mspace{14mu}{mid}\text{-}{ambles}},}\end{matrix}\mspace{14mu}} \\0 & {{otherwise}.}\end{matrix} \right.} & {{{Eq}.\mspace{14mu} 19}C}\end{matrix}$and at the receive side, when β=1, the number of mid-ambles N_(MA) isdetermined by either:

$\begin{matrix}{N_{MA} = \left\lfloor \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {2 + b_{{PE}\text{-}Disambiguity}} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rfloor} & {{{Eq}.\mspace{14mu} 30}C} \\{{or}\mspace{14mu}{by}} & \; \\{N_{MA} = \left\lceil \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {2 + b_{{PE}\text{-}Disambiguity} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rceil} & {{{Eq}.\mspace{14mu} 31}C}\end{matrix}$

Note that when β=1, the number of mid-ambles N_(MA) is 0 or a positiveinteger according to the definition wherein the number of mid-amblesN_(MA) is the number of mid-amble inserted on every M except two cases.There is no mid-amble inserted after the last OFDM data symbol ifmod(N_(SYM), N_(MA))=0, and at the end of an HE PPDU, if mod(N_(SYM),N_(MA))=1, there is also no mid-amble inserted before the last OFDM datasymbol. In an embodiment, 0 is a predetermined value.

In another embodiment, a process determines a number of OFDM datasymbols N_(SYM) and a Packet-extension duration T_(PE) for a received HEPPDU as follows:

When Doppler information for the HE PPDU indicates that one or moremid-ambles exist in the HE PPDU, the process determines a number ofmid-ambles N_(MA) according to:

$\begin{matrix}{N_{MA} = {\left\lfloor \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\{b_{{PE}\text{-}{Disambiguity}} + 1}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rfloor.}} & {{Eq}.\mspace{14mu} 32} \\{{or}\mspace{14mu}{according}\mspace{14mu}{{to}:}} & \; \\{N_{MA} = \left\lceil \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\{b_{{PE}\text{-}{Disambiguity}} + 1 - M}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rceil} & {{Eq}.\mspace{14mu} 33}\end{matrix}$Otherwise, when the Doppler information indicates no mid-ambles exist inthe HE PPDU, the number of mid-ambles N_(MA)=0.

The process then determines an estimated number of OFDM symbolsT_N_(SYM) used to decode data according to either:

$\begin{matrix}{{T_{-}N_{SYM}} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} - \left\lfloor {\frac{T_{MA}}{T_{SYM}} \cdot \left\lceil \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\{b_{{PE}\text{-}{Disambiguity}} + 1 - M}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rceil} \right\rfloor}} & {{Eq}.\mspace{14mu} 34} \\{\mspace{79mu}{or}} & \; \\{{T_{-}N_{SYM}} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} - \left\lfloor {\frac{T_{MA}}{T_{SYM}} \cdot \left\lfloor \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\{b_{{PE}\text{-}{Disambiguity}} + 1}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rfloor} \right\rfloor}} & {{Eq}.\mspace{14mu} 35}\end{matrix}$

The estimated number of OFDM symbols T_N_(SYM) needs to be verified bydetermining whether T_T_(PE) is less than 0 to obtain a final value forN_(SYM).

$\begin{matrix}{{T_{-}T_{PE}} = {\left\lfloor \frac{\begin{matrix}{\left( {{\frac{{L_{-}{LENGTH}} + m + 3}{3} \times 4} - T_{PA} - {N_{MA}T_{MA}}} \right) -} \\{T_{-}N_{SYM}T_{SYM}}\end{matrix}}{4} \right\rfloor \times 4}} & {{Eq}.\mspace{14mu} 36} \\{\mspace{79mu}{N_{SYM} = \left\{ \begin{matrix}{{T\_ N}_{SYM} - 1} & {{{{when}\mspace{14mu}{T\_ T}_{PE}} < 0},} \\{T\_ N}_{SYM} & {{otherwise}.}\end{matrix} \right.}} & {{Eq}.\mspace{14mu} 37}\end{matrix}$The PE duration T_(PE) is then determined according to Equation 6,above.

The equations 34-37 above, used to determine T_N_(SYM) and N_(SYM)above, are derived as follows in light of FIG. 19.

FIG. 19 illustrates features of a PPDU 1900 including a mid-amble 1908according to an embodiment. The PPDU 1900 also includes an L-SIG field1902, an HE Preamble 1904, first and second portions of a Data field1906-1 and 1906-2, and a Packet Extension (PE) 1910. A duration of theHE Preamble 1904 is indicated by T_(PA). A combined duration of themid-ambles of the PPDU is indicated by T_(HE_MIDAMBLE). A duration ofthe PE 1910 is indicated by T_(PE).

A length from the end of the L-SIG field 1902 to beyond an end of thePPDU is equal to a value L_LENGTH of a length field of the L-SIG field1902 plus a number of Service bits (16) at the beginning of the firstportion of the Data field 1906-1 plus a number of Tail bits (6) at theend of the last (here, second) portion of the Data field 1906-2 plus m,m is 1 for an HE MU PPDU or HE ER SU PPDU, and 2 otherwise.

In order to get N_(SYM) at the receive side, the equation below is usedwhen Doppler information is set to the first state (e.g. 1) whichindicates that the Mid-Amble exists:

$\begin{matrix}{{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} = {T_{PA} + {N_{SYM}T_{SYM}} + {N_{MA}T_{MA}} + T_{PE} + {T_{SYM}b_{{PE}\text{-}{Disambiguty}}} + \alpha}}\mspace{20mu}{{0 \leq \alpha < 4},{0 \leq {T_{PE} + \alpha} < T_{SYM}}}} & {{Eq}.\mspace{14mu} 38}\end{matrix}$

Step D1) from Equation 38 it follows that:

$\begin{matrix}{{{N_{SYM}T_{SYM}} + {N_{MA}T_{MA}} + {T_{SYM}b_{{PE}\text{-}{Disambiguty}}}} = {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - \left( {T_{PE} + \alpha} \right)}} & {{Eq}.\mspace{14mu} 39} \\{\left\lfloor {N_{SYM} + {N_{MA}\frac{T_{MA}}{T_{SYM}}} + b_{{PE}\text{-}{Disambiguty}}} \right\rfloor = \left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - \left( {T_{PE} + \alpha} \right)}{T_{SYM}} \right\rfloor} & {{Eq}.\mspace{14mu} 40} \\{{N_{SYM} + \left\lfloor {N_{MA}\frac{T_{MA}}{T_{SYM}}} \right\rfloor} = {\left\lfloor {\frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} - \frac{T_{PE} + \alpha}{T_{SYM}}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}}}} & {{Eq}.\mspace{14mu} 41}\end{matrix}$

Because T_(PE) is not known without N_(SYM) in a receiver of an HE PPDU,((T_(PE)+α)/T_(SYM)) is temporarily ignored, and the impact of this termwill be verified later. As shown in Equation 42, below, N_(SYM) isreplaced with T_N_(SYM) as a temporary number of OFDM data symbol:

$\begin{matrix}{{{T_{-}N_{SYM}} + \left\lfloor {N_{MA}\frac{T_{MA}}{T_{SYM}}} \right\rfloor} = {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}}}} & {{Eq}.\mspace{14mu} 42}\end{matrix}$

Step D2) from the above:T_N _(SYM) =M·N _(MA) +n ₀, 0≤n ₀ ≤M−1  Eq. 43

Step D3) from Step D1 and Step D2:

$\begin{matrix}{{{N_{MA}\frac{T_{MA}}{T_{SYM}}} = {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} - {T\_ N}_{SYM} + \alpha}},{0 \leq \alpha < 1}} & {{Eq}.\mspace{14mu} 44} \\{{\frac{{T\_ N}_{SYM} - n_{0}}{M} \cdot \frac{T_{MA}}{T_{SYM}}} = {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} - {T\_ N}_{SYM} + \alpha}} & {{Eq}.\mspace{14mu} 45} \\{{T\_ N}_{SYM} = {\frac{M}{{T_{MA}/T_{SYM}} + M} \cdot \left( {{\frac{T_{MA}/T_{SYM}}{M} \cdot n_{0}} + \left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} + \alpha} \right)}} & {{Eq}.\mspace{14mu} 45}\end{matrix}$

Step D4) from Step D2 and Step D3,

$\begin{matrix}{\mspace{79mu}{N_{MA} = \frac{{T\_ N}_{SYM} - n_{0}}{M}}} & {{Eq}.\mspace{14mu} 46} \\{N_{MA} = {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} + \alpha - n_{0}} \right)}} & {{Eq}.\mspace{14mu} 47} \\{\mspace{79mu}{{0 \leq \alpha < 1},{0 \leq n_{0} \leq {M - 1}}}} & \;\end{matrix}$

Step D5) find minimum value and maximum value of the number ofmid-ambles N_(MA) to find the boundary:

$\begin{matrix}{\mspace{79mu}{{{{Assuming}\mspace{14mu}\alpha} = 1},{n_{0} = 0},{{Max}_{N_{MA}} = {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} + 1} \right)}}}} & {{Eq}.\mspace{14mu} 48} \\{\mspace{79mu}{{{{Assuming}\mspace{14mu}\alpha} = 0},{n_{0} = {M - 1}},{{Min}_{N_{MA}} = {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} - M + 1} \right)}}}} & {{Eq}.\mspace{14mu} 49} \\{{\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} - M + 1} \right)} < N_{MA} < {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{sYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} + 1} \right)}} & {{Eq}.\mspace{14mu} 50}\end{matrix}$

Step D6) check (Max N_(MA)−Min N_(MA)) to see the range of N_(MA):

$\begin{matrix}{\left( {{{Max}N_{MA}} - {{Min}N_{MA}}} \right) = {\frac{M}{{T_{MA}/T_{SYM}} + M} < 1}} & {{Eq}.\mspace{14mu} 51}\end{matrix}$Since the number of mid-ambles N_(MA) is supposed to be a positiveinteger within 0<(MaxN_(MA)−MinN_(MA))<1, N_(NA) should be one positiveinteger, so floor(MaxN_(M))=ceil(MinN_(M)):

$\begin{matrix}\begin{matrix}{\quad{N_{MA} = \left\lfloor {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot} \right.}} \\{\left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor -} \right.} \\\left. \left. {b_{{PE}\text{-}{Disambiguty}} + 1} \right) \right\rfloor \\{= \left\lceil {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot} \right.} \\{\left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor -} \right.} \\\left. \left. {b_{{PE}\text{-}{Disambiguty}} - M + 1} \right) \right\rceil\end{matrix} & {{Eq}.\mspace{14mu} 52}\end{matrix}$Then, from the above equations,

$\begin{matrix}{{T\_ N}_{SYM} = {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} - \left\lfloor {N_{MA}\frac{T_{MA}}{T_{SYM}}} \right\rfloor}} & {{Eq}.\mspace{14mu} 53} \\{{T\_ N}_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} - \left\lfloor {\frac{T_{MA}}{T_{SYM}} \cdot \left\lceil \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\{b_{{PE}\text{-}{Disambiguty}} + 1 - M}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rceil} \right\rfloor}} & {{Eq}.\mspace{14mu} 54}\end{matrix}$Or

$\begin{matrix}{{T\_ N}_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} - \left\lfloor {\frac{T_{MA}}{T_{SYM}} \cdot \left\lfloor \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\{b_{{PE}\text{-}{Disamguty}} + 1}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rfloor} \right\rfloor}} & {{Eq}.\mspace{14mu} 55}\end{matrix}$

In another embodiment, a process determined the number of OFDM datasymbols N_(SYM) and a Packet-extension duration T_(PE) for a received HEPPDU is determined as follows:

When Doppler information for the HE PPDU indicates that one or moremid-ambles exist in the HE PPDU, the process determines a number ofmid-ambles N_(MA) according to:

$\begin{matrix}{N_{MA} = {\left\lfloor \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\b_{{PE}\text{-}{Disambiguty}}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rfloor.}} & {{Eq}.\mspace{14mu} 56}\end{matrix}$or according to:

$\begin{matrix}{N_{MA} = {\left\lceil \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\{b_{{PE}\text{-}{Disambiguty}} - M}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rceil.}} & {{Eq}.\mspace{14mu} 56}\end{matrix}$Otherwise, when the Doppler information indicates no mid-ambles exist inthe HE PPDU, the number of mid-ambles N_(MA)=0.

The process then determines an estimated number of OFDM symbolsT_N_(SYM) used to decode data according to either:

$\begin{matrix}{{T\_ N}_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor - b_{{{PE}\text{-}{Disambiguty}}} - \left\lfloor {\frac{T_{MA}}{T_{SYM}} \cdot \left\lceil \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\{b_{{PE}\text{-}{Disambiguty}} - M}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rceil} \right\rfloor}} & {{Eq}.\mspace{14mu} 57}\end{matrix}$or

$\begin{matrix}{{T\_ N}_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguty}} - \left\lfloor {\frac{T_{MA}}{T_{SYM}} \cdot \left\lfloor \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\b_{{PE}\text{-}{Disambiguty}}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rfloor} \right\rfloor}} & {{Eq}.\mspace{14mu} 58}\end{matrix}$

The estimated number of OFDM symbols T_N_(SYM) needs to be verified bydetermining whether T_T_(PE) is less than 0 to obtain a final value forN_(SYM).

$\begin{matrix}{{T\_ T}_{PE} = {\left\lfloor \frac{\begin{matrix}{\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - {N_{MA}T_{MA}}} \right) -} \\{{T\_ N}_{SYM}T_{SYM}}\end{matrix}}{4} \right\rfloor \times 4}} & {{Eq}.\mspace{14mu} 59} \\{\mspace{79mu}{N_{SYM} = \left\{ \begin{matrix}{{T\_ N}_{SYM} - 1} & {{{{when}\mspace{14mu}{T\_ T}_{PE}} < 0},} \\{T\_ N}_{SYM} & {{otherwise}.}\end{matrix} \right.}} & {{Eq}.\mspace{14mu} 60}\end{matrix}$The PE duration T_(PE) is then determined according to Equation 6,above.

The equations 57-60 above used to determine T_N_(SYM) and N_(SYM) aboveare derived as follows: In order to get N_(SYM) at the receive side, theequation below is used when Doppler information is set to the firststate (e.g. 1) which indicates that the Mid-Amble exists:

$\begin{matrix}{{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} = {T_{PA} + {N_{SYM}T_{SYM}} + {N_{MA}T_{MA}} + T_{PE} + {T_{SYM}b_{{PE}\text{-}{Disambiguty}}} + \alpha}}\mspace{20mu}{{0 \leq \alpha < 4},{0 \leq {T_{PE} + \alpha} < T_{SYM}}}} & {{Eq}.\mspace{14mu} 61}\end{matrix}$

Step E1) from Equation 61 it follows that:

$\begin{matrix}{{{N_{SYM}T_{SYM}} + {N_{MA}T_{MA}} + {T_{SYM}b_{{PE}\text{-}{Disambiguity}}}} = {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - \left( {T_{PE} + \alpha} \right)}} & {{Eq}.\mspace{14mu} 62} \\{\left\lfloor {N_{SYM} + {N_{MA}\frac{T_{MA}}{T_{SYM}}} + b_{{PE}\text{-}{Disambiguity}}} \right\rfloor = \left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} - \left( {T_{PE} + \alpha} \right)}{T_{SYM}} \right\rfloor} & {{Eq}.\mspace{14mu} 63} \\{{N_{SYM} + \left\lfloor {N_{MA}\frac{T_{MA}}{T_{SYM}}} \right\rfloor} = {\left\lfloor {\frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} - \frac{T_{PE} + \alpha}{T_{SYM}}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}}}} & {{Eq}.\mspace{14mu} 64}\end{matrix}$

Since T_(PE) is not known without N_(SYM) in a receiver of an HE PPDU,((T_(pE)+α)/T_(SYM)) is temporarily ignored, and the impact of this termwill be verified later. As shown in Equation 42, below, N_(SYM) isreplaced with T_N_(SYM) as a temporary number of OFDM data symbol:

$\begin{matrix}{{{T\_ N}_{SYM} + \left\lfloor {N_{MA}\frac{T_{MA}}{T_{SYM}}} \right\rfloor} = {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}}}} & {{Eq}.\mspace{14mu} 65}\end{matrix}$

Step E2) from the above:T_N _(SYM) =M·N _(MA) +n ₀+1, 0≤n ₀ ≤M−1  Eq. 66

Step E3) from Step E1 and Step E2:

$\begin{matrix}{{{N_{MA}\frac{T_{MA}}{T_{SYM}}} = {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} - {T\_ N}_{SYM} + \alpha}},{0 \leq \alpha < 1}} & {{Eq}.\mspace{14mu} 67} \\{{\frac{{T\_ N}_{SYM} - n_{0} - 1}{M} \cdot \frac{T_{MA}}{T_{SYM}}} = {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} - {T\_ N}_{SYM} + \alpha}} & {{Eq}.\mspace{14mu} 68} \\{{T\_ N}_{SYM} = {\frac{M}{{T_{MA}/T_{SYM}} + M} \cdot \left( {{\frac{T_{MA}/T_{SYM}}{M} \cdot \left( {n_{0} + 1} \right)} + \left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} + \alpha} \right)}} & {{Eq}.\mspace{14mu} 69}\end{matrix}$

Step E4) from Step E2 and Step E3,

$\begin{matrix}{\mspace{79mu}{N_{MA} = \frac{{T\_ N}_{SYM} - 1 - n_{0}}{M}}} & {{Eq}.\mspace{14mu} 70} \\{{N_{MA} = {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} + \alpha - n_{0} - 1} \right)}}\mspace{79mu}{{0 \leq \alpha < 1},{0 \leq n_{0} \leq {M - 1}}}} & {{Eq}.\mspace{14mu} 71}\end{matrix}$

Step E5) find minimum value and maximum value of N_(MA) to find theboundary:

$\begin{matrix}{\mspace{79mu}{{{{Assuming}\mspace{14mu}\alpha} = 1},{n_{0} = 0},{{Max}_{N_{MA}} = {\frac{1}{{T_{MA}/T_{SYM}} + M}.\left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}}} \right)}}}} & {{Eq}.\mspace{14mu} 72} \\{\mspace{79mu}{{{{Assuming}\mspace{14mu}\alpha} = 0},{n_{0} = {M - 1}},{{Min}_{N_{MA}} = {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} - M} \right)}}}} & {{Eq}.\mspace{14mu} 73} \\{{\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} - M} \right)} < N_{MA} < {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}}} \right)}} & {{Eq}.\mspace{14mu} 74}\end{matrix}$

Step E6) Step D6) check (MaxN_(MA)−MinN_(MA)) to see the range ofN_(MA):

$\begin{matrix}{\left( {{{Max}\; N_{MA}} - {{Min}\; N_{MA}}} \right) = {\frac{M}{{T_{MA}/T_{SYM}} + M} < 1}} & {{Eq}.\mspace{14mu} 75}\end{matrix}$Since N_(NA) is supposed to be a positive integer within0<(MaxN_(MA)−MinN_(MA))<1, N_(MA) should be a positive integer, sofloor(MaxN_(MA))=ceil(MinN_(MA)):

$\begin{matrix}\begin{matrix}{N_{MA} = \left\lfloor {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot} \right.} \\\left. \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}}} \right) \right\rfloor \\{= \left\lceil {\frac{1}{{T_{MA}/T_{SYM}} + M} \cdot} \right.} \\\left. \left( {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} - M} \right) \right\rceil\end{matrix} & {{Eq}.\mspace{14mu} 76}\end{matrix}$

Then, from the above equations,

$\begin{matrix}{{{T\_ N}_{SYM} = {\left\lfloor \frac{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}}{T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} - \left\lfloor {N_{MA}\frac{T_{MA}}{T_{SYM}}} \right\rfloor}},{and}} & {{Eq}.\mspace{14mu} 77} \\{{{T\_ N}_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} - \left\lfloor {\frac{T_{MA}}{T_{SYM}} \cdot \left\lceil \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\{b_{{PE}\text{-}{Disambiguity}} - M}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rceil} \right\rfloor}},} & {{Eq}.\mspace{14mu} 78}\end{matrix}$or

$\begin{matrix}{{T\_ N}_{SYM} = {\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor - b_{{PE}\text{-}{Disambiguity}} - {\left\lfloor {\frac{T_{MA}}{T_{SYM}} \cdot \left\lfloor \frac{\begin{matrix}{\left\lfloor {\left( {{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA}} \right)/T_{SYM}} \right\rfloor -} \\b_{{PE}\text{-}{Disambiguity}}\end{matrix}}{{T_{MA}/T_{SYM}} + M} \right\rfloor} \right\rfloor.}}} & {{Eq}.\mspace{14mu} 79}\end{matrix}$

In another embodiment of the invention, when an HE PPDU is receivedwherein the Doppler information is set to indicate that one or moremid-ambles exist, if signal loss occurs during reception prior tocompletion of reception of the PSDU, the error conditionPHYRXEND.indication(CarrierLost) shall be reported to the MAC. Afterwaiting for the end of the PPDU as determined by Equation 80, below, thePHY shall set the PHY-CCA.indication (IDLE) primitive and return to theRX IDLE state.RXTIME=20+T _(PA) +N _(SYM) T _(SYM) +N _(MA) T _(MA) +T _(PE) +SET _(MA) =N _(HE-LTF) T _(HE-LTF)+(T _(HE-STF))  Eq. 80Note that the duration of HE-STF T_(HE-STF) could be omitted fromEquation 20.

FIG. 21 illustrates a process 2100, according to an embodiment, forreceiving a PPDU having a data field that includes mid-ambles. Thesymbols may be symbols in a data field of the PPDU into which mid-amblesare inserted. The process 2100 may be performed by a wireless deviceincluding a receiver, and the wireless device may include a processorconfigured to perform the process 2100.

At S2102, the process 2100 determines a format of a PPDU being received.Determining the format of the PPDU being received may include receivinga first four symbols starting with L-STF of the PPDU being received,determining a modulation method of the third and fourth symbols of thereceived symbols, and determining whether the contents of the fourthsymbol is the same as the contents of the third symbol. The third symbolmay be a symbol of a Legacy Signal (L-Sig) field.

When the third and fourth symbols are modulated using BPSK, the thirdsymbol is an L-SIG field symbol, and the fourth symbol carries aduplicate of the contents of the L-SIG field, the PPDU being received isan HE PPDU, and determining the format may further include receivingfifth and sixth symbols, and determining the format of the PPDU beingreceived according to a value of a Length field of the L-SIG fieldmodulo 3 and the modulation methods of the fifth and sixth symbols, asdescribed with respect to FIG. 12.

At S2104, the process 2100 determines whether the PPDU being received isan HE PPDU. In response to determining that the PPDU being received isan HE PPDU, at S2104 the process 2100 proceeds to S2106; otherwise theprocess 2100 exits.

At S2106, the process 2100 determines whether the PPDU being received isan HE Multi-User (MU) or HE Extended Range Single User (ER SU) PPDU. Inresponse to determining that the PPDU being received is either an HE MUPPDU or an HE ER SU PPDU, at S2106 the process 2100 proceeds to S2110;otherwise the process 2100 proceeds to S2108.

At S2108, the process S2100 sets a modifier m to 1 in response to thePPDU being received being neither an HE MU PPDU nor an HE ER SU PPDU,then proceeds to S2112.

At S2110, the process S2100 sets a modifier m to 2 in response to thePPDU being received being either an HE MU PPDU or an HE ER SU PPDU, thenproceeds to S2112.

At S2112, the process S2100 decodes an HE Signal A (HE-SIG-A) field.When the PPDU being received is an HE ER SU PPDU, decoding the HE-SIG-Afield includes receiving and decoding the fifth through eighth symbolsof the PPDU being received. When the PPDU being received is an HE MUPPDU, an HE TB PPDU, or an HE SU PPDU, decoding the HE-SIG-A fieldincludes receiving and decoding the fifth through sixth symbols of thePPDU being received.

At S2114, the process S2100 determines whether the HE-SIG-A fieldindicates that the PPDU being received include mid-ambles. In anembodiment, the process S2100 determines that the PPDU being receivedincludes mid-ambles in response to a Doppler field of the HE-SIG-A fieldhas a value (for example, 1) corresponding to a first state, anddetermines that the PPDU being received does not include mid-ambles whenthe Doppler field does not have the value corresponding to the firststate (i.e., has a value other than the value corresponding to the firststate.)

In response to determining that the PPDU being received includesmid-ambles, at S2114 the process 2100 proceeds to S2116; otherwise theprocess 2100 exits.

At S2116, the process 2100 determines values of an L-SIG Length fieldL_LENGTH, a Packet Extension (PE) Disambiguity bit b_(PE-Disambiguity),an HE-LTF duration T_(HE-LTF), a preamble duration T_(PA), a mid-ambleduration T_(MA), a duration of a symbol of a data field of the PPDUbeing received T_(SYM) (hereinafter, data symbol duration T_(SYM)), anda mid-amble periodicity M.

The process 2100 determines the value of the L-SIG Length field L_LENGTHusing the received L-SIG field of the PPDU being received. The process2100 determines the values of the PE Disambiguity bitb_(PE-Disambiguity), the mid-amble periodicity M, and the data symbolduration T_(SYM) using information in the HE-SIG-A field in accordancewith an applicable standard. In an embodiment, the applicable standardis the IEEE Std 802.11ax or a successor thereto.

The process 2100 determines the HE-LTF duration T_(HE-LTF) correspondingto the duration of HE-LTFs included in the PPDU being received usinginformation in the HE-SIG-A field in accordance with the applicablestandard. As used herein, the HE-LTF duration T_(HE-LTF) includes aduration of a guard interval included in each HE-LTF.

The process 2100 determines the value of the preamble duration T_(PA) asbeing equal to a sum of a duration of the RL-SIG field (4 μs), aduration of the HE-SIG-A field (16 μs for an HE ER SU PPDU, 8 μsotherwise), a duration of an HE-SIG-B field if present (variable), aduration of an HE-STF (8 μs for an HE TB PPDU, 4 μs otherwise), and thecombined durations of one or more HE-LTFs immediately following theHE-STF (hereinafter, the number of which is referred to as a number ofHE-LTFs N_(HE-LTF)). The process 2100 determines the number of HE-LTFsN_(HE-LTF) using information in the HE-SIG-A field in accordance withthe applicable standard.

The process 2100 determines the value of the mid-amble duration T_(MA)according to the product of the number of HE-LTFs N_(HE-LTF) and theHE-LTF duration T_(HE-LTF), as prescribed in the applicable standard:T _(MA) =N _(HE-LTF) ·T _(HE-LTF)  Eq. 81

At S2118, the process 2100 determines a value of a number of mid-amblesN_(MA) using the values determined at S2116. In an embodiment, the valueof the number of mid-ambles N_(MA) is determined according to Equation30B, above, using a value of β prescribed by the applicable standard,wherein β is an integer value greater than or equal to zero indicating anumber of data symbols in excess of the mid-amble periodicity M allowedat the end of a data field without requiring the insertion of anothermid-amble. In an embodiment, the value of the number of mid-amblesN_(MA) is determined according to Equation 31B, above, using the valueof β prescribed by the applicable standard. In embodiments, the value ofβ is 0. In other embodiments, the value of β is 1.

At S2120, the process 2100 determines a value of number of data symbolsN_(SYM) and a value of a PE duration T_(PE). In an embodiment, theprocess 2100 determines the value of the number of data symbols N_(SYM)according to Equation 5, above, and then determines the value of the PEduration T_(PE) according to Equation 6, above.

At 2122, the process 2100 receives a data field of the PPDU beingreceived using the information determined in S2102 through S2120.Receiving the data field may include iteratively receiving a number ofdata symbols equal to the mid-amble periodicity M and a mid-amble thatimmediately follows the data symbols until the number of mid-amblesreceived is equal to the number of mid-ambles N_(MA) determined atS2118. Each mid-amble consists of N_(HE-LTF) HE-LTFs.

Once the iterations are complete, the remaining data symbols are thenreceived. The process 2100 then exits. The number of remaining datasymbols N_(remain) isN _(remain) =N _(SYM)−(M·N _(MA))  Eq. 82

FIG. 22 illustrates a process 2222, according to an embodiment, forreceiving a data field of a PPDU including mid-ambles. The process 2222may be performed in S2122 of the process 2100 of FIG. 21.

At S2202, the process 2222 initializes a loop counter N_(MA) to 1. AtS2204, the process 2222 receives an N^(th) plurality of consecutive datasymbols, wherein the number of data symbols in each plurality ofconsecutive data symbols equals the mid-amble periodicity M.

At S2206, the process 2222 receives an N^(th) mid-amble. At S2208, theprocess 2222 increments the loop counter N_(MA) by 1.

At S2210, in response to the loop counter N_(MA) having a value lessthan or equal to a value of the number of mid-ambles N_(MA) M, theprocess 2222 proceeds to S2204; otherwise at S2210 the process 2222proceeds to S2212.

At S2212, the process 2222 receives the remaining data symbols. Thenumber of remaining data symbols may be determined according to Equation82, above.

The solutions provided herein have been described with reference to awireless LAN system; however, it should be understood that thesesolutions may also be applicable to other network environments, such ascellular telecommunication networks, wired networks, and so on.

The above explanation and figures are applied to an HE station, an HEframe, an HE PPDU, an HE-SIG field and the like of the IEEE 802.11axamendment, but they can also applied to a receiver, a frame, PPDU, a SIGfield, and the like of another future amendment of IEEE 802.11.

Embodiments of the present disclosure include electronic devicesconfigured to perform one or more of the operations described herein.However, embodiments are not limited thereto.

Embodiments of the present disclosure may further include systemsconfigured to operate using the processes described herein. The systemsmay include basic service sets (BSSs) such as the BSSs 100 of FIG. 1,but embodiments are not limited thereto.

Embodiments of the present disclosure may be implemented in the form ofprogram instructions executable through various computer means, such asa processor or microcontroller, and recorded in a non-transitorycomputer-readable medium. The non-transitory computer-readable mediummay include one or more of program instructions, data files, datastructures, and the like. The program instructions may be adapted toexecute the processes and to generate and decode the frames describedherein when executed on a device such as the wireless devices shown inFIG. 1.

In an embodiment, the non-transitory computer-readable medium mayinclude a read only memory (ROM), a random access memory (RAM), or aflash memory. In an embodiment, the non-transitory computer-readablemedium may include a magnetic, optical, or magneto-optical disc such asa hard disk drive, a floppy disc, a CD-ROM, and the like.

In some cases, an embodiment of the invention may be an apparatus (e.g.,an AP station, a non-AP station, or another network or computing device)that includes one or more hardware and software logic structure forperforming one or more of the operations described herein. For example,as described above, the apparatus may include a memory unit, whichstores instructions that may be executed by a hardware processorinstalled in the apparatus. The apparatus may also include one or moreother hardware or software elements, including a network interface, adisplay device, etc.

While this invention has been described in connection with what ispresently considered to be practical embodiments, embodiments are notlimited to the disclosed embodiments, but, on the contrary, may includevarious modifications and equivalent arrangements included within thespirit and scope of the appended claims. The order of operationsdescribed in a process is illustrative and some operations may bere-ordered. Further, two or more embodiments may be combined.

What is claimed is:
 1. A method performed by a wireless device, themethod comprising: receiving a first portion of a PHY Protocol Data Unit(PPDU), the first portion including a Legacy Signal (L-SIG) field;decoding the L-SIG field; determining a format of the PPDU using thefirst portion; and in response to determining that the format of thePPDU is a High Efficiency (HE) format: receiving and decoding an HESignal A (HE-SIG-A) field, determining, using a Doppler field of theHE-SIG-A field, whether the PPDU includes mid-ambles, and in response todetermining that the PPDU includes mid-ambles: determining, according tothe format of the PPDU and using first information determined using theHE-SIG-A field and second information determined using the L-SIG field,a number of mid-ambles N_(MA) indicating a total number of mid-amblesincluded in a data field of the PPDU; determining, using the number ofthe mid-ambles N_(MA), a number of data symbols N_(SYM) indicating atotal number of data symbols included in the data field of the PPDU; andreceiving, using the number of mid-ambles N_(MA) and the number of datasymbols N_(SYM), the data field of the PPDU.
 2. The method of claim 1,wherein the first information includes a Packet Extension (PE)Disambiguity bit value b_(PE-Disambiguity), a number of HE Long TrainingFields (HE-LTFs) value N_(HE-LTF), an HE-LTF duration including guardinterval T_(HE-LTF), and a data symbol duration T_(SYM), and a mid-ambleperiodicity M.
 3. The method of claim 2, wherein the first informationfurther includes a preamble duration T_(PA) according to the format ofthe PPDU, the HE-LTF duration T_(HE-LTF), and the number of HE-LTFsvalue N_(HE-LTF).
 4. The method of claim 3, wherein the firstinformation further includes a mid-amble duration T_(MA).
 5. The methodof claim 4, wherein the second information includes a Length field valueL_LENGTH.
 6. The method of claim 5, wherein determining the number ofmid-ambles N_(MA) includes determining the number of mid-ambles N_(MA)according to: $N_{MA} = \left\lfloor \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}{Disambiguity}}} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rfloor$ wherein m is 1when the format of the PPDU is an HE Multi-User PPDU or HE ExtendedRange Single User PPDU format and m is 2 otherwise, and wherein β is aninteger number greater than or equal to zero.
 7. The method of claim 6,wherein β is
 1. 8. The method of claim 5, wherein determining the numberof mid-ambles N_(MA) includes determining the number of mid-amblesN_(MA) according to: $N_{MA} = \left\lceil \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}{Disambiguity}} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rceil$ wherein m is 1when the format of the PPDU is an HE Multi-User PPDU or HE ExtendedRange Single User PPDU format and m is 2 otherwise, and wherein β is aninteger number greater than or equal to zero.
 9. The method of claim 8,wherein β is
 1. 10. The method of claim 1, wherein receiving the datafield comprises: repeating, a number of times equal to the number ofmid-ambles N_(MA): receiving a plurality of consecutive data symbols,wherein the number of data symbols in the plurality of data symbols isequal to the mid-amble periodicity M, and receiving a mid-ambleimmediately following the plurality of consecutive data symbols; andreceiving a remaining 0 or more remaining consecutive data symbols,wherein the number of data symbols N_(remain) is equal to:N _(remain) =N _(SYM)−(M·N _(MA)).
 11. A wireless device comprising: areceiver; and a processor, the processor configured to perform:receiving, using the receiver, a first portion of a PHY Protocol DataUnit (PPDU), the first portion including a Legacy Signal (L-SIG) field;decoding the L-SIG field; determining a format of the PPDU using thefirst portion; and in response to determining that the format of thePPDU is a High Efficiency (HE) format: receiving and decoding an HESignal A (HE-SIG-A) field, determining, using a Doppler field of theHE-SIG-A field, whether the PPDU includes mid-ambles, and in response todetermining that the PPDU includes mid-ambles: determining, according tothe format of the PPDU and using first information determined using theHE-SIG-A field and second information determined using the L-SIG field,a number of mid-ambles N_(MA) indicating a total number of mid-amblesincluded in a data field of the PPDU; determining, using the number ofthe mid-ambles N_(MA), a number of data symbols N_(SYM) indicating atotal number of data symbols included in the data field of the PPDU; andreceiving, using the number of mid-ambles N_(MA) and the number of datasymbols N_(SYM), the data field of the PPDU.
 12. The wireless device ofclaim 11, wherein the first information includes a Packet Extension (PE)Disambiguity bit value b_(PE-Disambiguity), a number of HE Long TrainingFields (HE-LTFs) value N_(HE-LTF), an HE-LTF duration including guardinterval T_(HE-LTF), and a data symbol duration T_(SYM), and a mid-ambleperiodicity M.
 13. The wireless device of claim 12, wherein the firstinformation further includes a preamble duration T_(PA) according to theformat of the PPDU, the HE-LTF duration T_(HE-LTF), and the number ofHE-LTFs value N_(HE-LTF).
 14. The wireless device of claim 13, whereinthe first information further includes a mid-amble duration T_(MA). 15.The wireless device of claim 14, wherein the second information includesa Length field value L_LENGTH.
 16. The wireless device of claim 15,wherein determining the number of mid-ambles N_(MA) includes determiningthe number of mid-ambles N_(MA) according to:$N_{MA} = \left\lfloor \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}{Disambiguity}}} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rfloor$ wherein m is 1when the format of the PPDU is an HE Multi-User PPDU or HE ExtendedRange Single User PPDU format and m is 2 otherwise, and wherein β is aninteger number greater than or equal to zero.
 17. The wireless device ofclaim 16, wherein β is
 1. 18. The wireless device of claim 15, whereindetermining the number of mid-ambles N_(MA) includes determining thenumber of mid-ambles N_(MA) according to:$N_{MA} = \left\lceil \frac{\begin{matrix}{{\frac{{L\_ LENGTH} + m + 3}{3} \times 4} - T_{PA} -} \\{T_{SYM}\left( {1 + \beta + b_{{PE}\text{-}{Disambiguity}} + M} \right)}\end{matrix}}{T_{MA} + {M \cdot T_{SYM}}} \right\rceil$ wherein m is 1when the format of the PPDU is an HE Multi-User PPDU or HE ExtendedRange Single User PPDU format and m is 2 otherwise, and wherein β is aninteger number greater than or equal to zero.
 19. The wireless device ofclaim 18, wherein β is
 1. 20. The wireless device of claim 11, whereinreceiving the data field comprises: repeating, a number of times equalto the number of mid-ambles N_(MA): receiving a plurality of consecutivedata symbols, wherein the number of data symbols in the plurality ofdata symbols is equal to the mid-amble periodicity M, and receiving amid-amble immediately following the plurality of consecutive datasymbols; and receiving a remaining 0 or more remaining consecutive datasymbols, wherein the number of data symbols N_(remain) is equal to:N _(remain) =N _(SYM)−(M·N _(MA)).